Old time mechanic question..

Discussion in 'The Garage' started by Lager, May 23, 2020.

  1. Lager

    Lager Active Member

    Joined:
    Aug 3, 2017
    Messages:
    602
    Likes Received:
    912
    Location:
    Salisbury NC
    Ive got a 1975 Chev pickup camper special that has a 454 ,TH-400 trans and a 373 rear end. Ive owned this truck for the past 35 years and is as original as can be. I decided to give the old engine an up grade with an new carb, intake, cam, headers in the effort to improve its stock 230 HP and 450 tork. So I started with a compression test to determine health, all 8 cylinders came up with 85 PSI. This seemed to me a bit low so I checked the calibration of my tester with my air compressor and its reads correctly. So, I did a wet test and it only increased by 3 PSI. So, Im thinking that 85 PSI is normal for a 8-1 compression 1975 chev engine.. Any experience out there that confirms my results as being normal ? My truck runs great, 20 year old spark plugs show no signs of oil fowling, there has been no oil consumption in the past 20 years. Yes, today I did its first oil change in 20 years.. I only drive it twice a year to go to Lowes to get wood or something...But, all of a sudden I feel the need to build something and this old truck is what I have.. So is this compression pressure correct for this old truck ?
     
  2. Johnny

    Johnny Misanthropist Supporting Member

    Joined:
    Dec 19, 2016
    Messages:
    10,037
    Likes Received:
    61,899
    Location:
    Pender County
    Cold compression testing isn't a good indicator for much besides comparing one cylinder to another and even then battery voltage needs to be the same throughout the test.
    If you really want to see the health of an engine you want to do a leak down test. A leakdown test requires another tool but they aren't all that expensive, you will also need an air compressor.
     
    BatteryOaksBilly, Pink_Vapor and Rob like this.
  3. Lager

    Lager Active Member

    Joined:
    Aug 3, 2017
    Messages:
    602
    Likes Received:
    912
    Location:
    Salisbury NC
    Yep you are correct, I have a leakdown tester and an air compressor,, just ran out of time tonight. But I was able to do a wet test and that would have determined the piston ring seal was worn, but it didnt.. The leakdown test would have confirmed a valve leak, but whats the chance of every cylinder having the same valve leakage ?? But, I appreciate your response..
     
    Johnny likes this.
  4. Mike Overlay

    Mike Overlay Lacks seriousness Staff Member Benefactor Charter Life Member

    Joined:
    Dec 18, 2016
    Messages:
    5,765
    Likes Received:
    16,712
    Location:
    gtown nc
    That is not to far from normal for the old 454 torque motors. A set of higher compression heads, and flat top pistons would give it more gitty up bang per buck
     
    Last edited: May 23, 2020
    fieldgrade and gunbelt like this.
  5. Sharps40

    Sharps40 Price, it's all about the price

    Joined:
    Dec 18, 2016
    Messages:
    1,180
    Likes Received:
    1,632
    Location:
    South Centralish NC.
    120-180 psi is more normal on a healthy v8. Anything below 100 psi is considered very low.

    Your wet/dry results indicate no significant ring or valve failures. Prolly all leaking a bit from wear. 1st gen chevy engines were basically 100k or less motors.

    Prolly very driveable and reliable, but....

    At a balanced 85 psi it's not making factory hp or torque.

    I'd consider it worn. Goodas is, (if reliable), but tired and not ready for your proposed upgrades.

    If it were mine I'd open it, check out ridges, valves bearings, etc, freshen it up with a rebuild since what you have planned in your first post is an expensive upgrade.


    Compression ratio and compression psi are not tied together e.g. 8 to 1 engine or 11 to 1 engine tells one nothing much about the pressure it will make.
     
    Last edited: May 24, 2020
    gunbelt likes this.
  6. Rob

    Rob Active Member Benefactor Life Member

    Joined:
    Aug 1, 2017
    Messages:
    574
    Likes Received:
    841
    Location:
    Wilmington, NC
    Last edited: May 24, 2020
    Burt Gummer likes this.
  7. Pink_Vapor

    Pink_Vapor “Not as funny as he thinks he is”- wife Supporting Member

    Joined:
    Jul 1, 2017
    Messages:
    7,213
    Likes Received:
    9,506
    Location:
    Moncure, NC
    Pressure being that low means it’s a perfect setup for supercharging :D

    I’m having a hard time understanding that, correct me if I’m off.
    If sea level air pressure is ~29psi, in a perfect theoretical scenario, 8:1 =232psi, 11:1=319.
    I bored my bike out 2mm & had 185psi, I added a 0.038” gasket & it dropped to ~125. Plus it was A LOT easier to kick start.
     
    Last edited: May 24, 2020
  8. Beef15

    Beef15 B or somesuch

    Joined:
    Dec 16, 2016
    Messages:
    2,478
    Likes Received:
    2,560
    Location:
    Forsyth
    Valve timing and duration complicates the formula.
     
    stickman61 likes this.
  9. rdinatal

    rdinatal Well-Known Member Supporting Member

    Joined:
    Dec 28, 2016
    Messages:
    5,835
    Likes Received:
    8,837
    Location:
    Lake Normanopolis, NC
    This may give you an idea to extrapolate when using your variables:

    5444_815_1501.png

    85psi seems a little low.
     
    Last edited: May 24, 2020
  10. Pink_Vapor

    Pink_Vapor “Not as funny as he thinks he is”- wife Supporting Member

    Joined:
    Jul 1, 2017
    Messages:
    7,213
    Likes Received:
    9,506
    Location:
    Moncure, NC
    Agreed, since it was a factory 80's engine, I left out valve overlap, etc.
     
  11. Lager

    Lager Active Member

    Joined:
    Aug 3, 2017
    Messages:
    602
    Likes Received:
    912
    Location:
    Salisbury NC
    [​IMG]
    Shaun H-A

    Lv 7
    9 years ago
    Favorite Answer
    Those are low numbers. If you are questioning ring seal, you should be checking that with a dual gauge leak down tester, not a compression gauge.



    Where the cam is phased (Advanced or Retarded) plays a huge role in cranking compression numbers and so does rocker arm adjustment. I've seen cranking compression numbers move as much as 50 PSI by simply advancing or retarding the cam. I routinely see 20 PSI on normal every day stuff. The chain retards the cam as it stretches. Plus, the factory cams were installed retarded because doing so help tweak the idle emissions. Other than that, retarding the cam for how the stock engine was used was a complete loss.



    If the rocker arms have never been touched, loosen every one of them exactly 1/2 turn. They will still be within factory spec. I would replace the timing chain with this: http://www.summitracing.com/parts/SUM-G6610-B/ this: http://www.summitracing.com/parts/SUM-G002/ and this: http://www.summitracing.com/parts/SUM-G1792/



    Install the crank gear at the 2 degree advance mark IF you are keeping the stock cam in the engine. The timing chain I have specified has a built in thrust plate on the back of the cam gear because timing gears on Big Block Chevy's LOVE to eat the block from the cam gear rubbing against it. Plus, the thrust washer positively locates the cam in the block so the cam lobes are centered with the lifter bores.



    Use a harmonic balancer puller to remove the balancer and use a harmonic balancer installer to install it again. DO NOT hammer the balancer back on the crankshaft with a hammer. You will destroy the rear thrust on the rear main bearing and also destroy the balancer. You will need to drop the oil pan down about 1/4-1/2 inch so the timing cover will line back up with the pan and gasket. Do not over torque the bolts on the pan or timing cover.



    After you replace the timing chain, I bet you see a 20-30 PSI gain in cranking compression.

    I bet you also see a 15-20 PSI gain with your rocker arm adjustment which will also be a very noticeable gain in both drive ability/performance AND fuel economy.



    FYI: I make a cam for this engine that is close to a 100 HP and 100FT lb torque gain over the stock cam, is a mileage improvement and it idles almost undetectable. It is a power improvement over the stock cam even from idle and of course throughout the entire RPM range. I'll make you a 100% money back guarantee on the cam as well. Love it or I will refund you. All designed to work with stock parts but I would suggest a valve spring change if you do it. I can give you a valve spring for it as well.

    Use a 3 arm puller to remove the old crank gear. Just be sure to protect the threads in the front of the crankshaft.



    Email: camshaftshaun@gmail.com

    While I am still going to perform a leak test today to determine if there is any excessive leakage, I started to think of cam timing and how it effects compression pressure.. Then I found this ?
     
    Button Pusher likes this.
  12. stickman61

    stickman61 Shakiest gun in the West Charter Life Member

    Joined:
    Dec 17, 2016
    Messages:
    463
    Likes Received:
    566
    Location:
    Burke County
    This.

    A 45 year old timing chain probably has the cam turned back pretty far too.
     
    Button Pusher and Mike Overlay like this.
  13. Scsmith42

    Scsmith42 Member Benefactor Charter Life Member Supporting Member

    Joined:
    Dec 17, 2016
    Messages:
    1,986
    Likes Received:
    4,228
    Location:
    New Hill, NC
    I used to do a lot of trucks like that back when I had my shop.

    Headers, dual exhaust, intake and good carb will really wake up the old 454’s. Add in a good low/midrange cam and you’re set.

    Doing it today though, if budget wasn’t an issue I’d go with an EFI setup instead of a carb. Much better power.

    And yes, 85 psi compression is low. Normal range (As I recall) is 125 - 150 for that engine. TheY had a problem with cylinder wear; if you opt to re-ring it be sure to use a ridge reamer or have the cylinders properly honed. If you use a ball style hone be sure that the ring ridge is totally removed or you’ll probably break a ring.
     
    Lager and Pink_Vapor like this.
  14. Sharps40

    Sharps40 Price, it's all about the price

    Joined:
    Dec 18, 2016
    Messages:
    1,180
    Likes Received:
    1,632
    Location:
    South Centralish NC.

    Keep my statement in context, Ratio tells you "Nothing Much". If you just want to know that as a general rule of thumb/to expect higher compression pressure, then higher compression ratio will usually get you there. Ratio is an easy calculation of the relationship between room in the cylinder at BDC compared to TDC. However, any given compression ratio number dosn't usually equal a hard/fast psi number. EG 8 to 1 is not automatically 135 PSI or any other number. An engineer may be able to calculate what the psi should be in a perfect world given all the variables in the motor are known, but he still won't know the real compression pressure until its measured.

    On the average naturally aspirated internal combustion engine, 135 psi cylinder pressure is about ideal as a general rule of thumb...(though some need higher, some need lower depnding on the entire package of engine components) and any cylinder pressures below 100 psi, as a general rule of thumb are not ideal and provide poor efficiency and lower power and on opening the/this engine will likely exhibit wear and tear, failed components, etc..

    At an even 85 psi cranking pressure, the noted 35 year old engine could well want an overhaul.

    The planned upgrades for the motor are expensive and would be a shame to spend several thousand in parts and labor on a motor that dosn't currently make the compression/power/torque that it had when newer or potentially less worn out. Point being: probably ought not to spend the money until the rest of the motor is vetted and potentially brought back up to at least factory new capaility.

    Press on with pride. I'm back to the garage tweaking Ol Bessy!
     
    Last edited: May 24, 2020
  15. John

    John Member Benefactor Charter Life Member

    Joined:
    Dec 18, 2016
    Messages:
    405
    Likes Received:
    354
    Location:
    Rutherford Co., NC
    Did you take out all the spark plugs when you did the tests? That may be a little low but not terrible, and them all being so even is a very good sign. Advertised as 8:1, the actual comp ratio is probably at least 1/2 point lower.

    With any car project, the most important thing is decide on a budget, and go from there.
     
  16. Pink_Vapor

    Pink_Vapor “Not as funny as he thinks he is”- wife Supporting Member

    Joined:
    Jul 1, 2017
    Messages:
    7,213
    Likes Received:
    9,506
    Location:
    Moncure, NC
    Agreed & understood.
    I was only scratching my head at, “Compression ratio and compression psi are not tied together”.
     
    Sharps40 likes this.
  17. Sharps40

    Sharps40 Price, it's all about the price

    Joined:
    Dec 18, 2016
    Messages:
    1,180
    Likes Received:
    1,632
    Location:
    South Centralish NC.
    Cool. Its a loose relationship.

    Sorta like you are Compression Ratio (Husband) stating we are going this way and thats it.

    But your Wife is Compression Pressure, and she go's up and down depending on any number of variables in a particular moment.
     
    Last edited: May 24, 2020
  18. Pink_Vapor

    Pink_Vapor “Not as funny as he thinks he is”- wife Supporting Member

    Joined:
    Jul 1, 2017
    Messages:
    7,213
    Likes Received:
    9,506
    Location:
    Moncure, NC
    If my engine was that unpredictable, I’d sell it.:p
     
    Last edited: May 24, 2020
    Sharps40 likes this.
  19. BowWow

    BowWow Happy to be here

    Joined:
    Jan 6, 2017
    Messages:
    2,803
    Likes Received:
    3,800
    Location:
    NC
    ………anything under 100 is on the low side...………

    If you're going to do all the work to the top end, you might as well do some work to the bottom end. You can make those big blocks scream, but everything seems to be much more expensive for the big blocks.
     
  20. OldNascar

    OldNascar Well-Known Member

    Joined:
    Dec 30, 2017
    Messages:
    1,163
    Likes Received:
    1,065
    Location:
    Statesville, NC
    Haven't read all the posts, I know Chevy retarded the cam around 1973 on the 350's and figure the same was done on the big block. Pull a valve cover and watch the intake valve as it opens, nominal would be 10-30 degrees BEFORE top dead center.I used to set the cam up a tooth or two advanced and the motor would pick up considerable compression.
     
  21. Coltdefender1911

    Coltdefender1911 On the couch Charter Member Supporting Member

    Joined:
    Dec 20, 2016
    Messages:
    3,839
    Likes Received:
    3,674
    Location:
    Charlotte, NC
    Fix your foundation before building your house. Pull her down and at least inspect/measure. I’ll bet she’s worn and wanting a refresh.
     
    LizardKing likes this.
  22. Lager

    Lager Active Member

    Joined:
    Aug 3, 2017
    Messages:
    602
    Likes Received:
    912
    Location:
    Salisbury NC
    First of all, I want to thank everyone for their comments or suggestions.. I bought this truck about 35 years ago to tow a race car trailer all around the South east when I followed the NHRA and Ford racing circuit and it did very well. This truck is about as original as you could possibly find.. Fast forward to today,, the old Quadra jet is done worn out.. The primary bushings are shot causing a high idle. So I started to look into a replacement, Found a Holley 750 vacuum secondary for $125. Since the Holley wont fit the stock intake with out an adapter, well, they cost too. Found a used Edelbrock dual plane for $100 so I might as well upgrade ? Headers are cheap for this truck,, $139 from Summit or Jegs.. Might as well upgrade them too ?
    Then we get to the health of the engine itself to see if the upgrades are worth it ? The 85 PSI had me concerned, but good news was that all cylinders were exactly the same. Another thing I noticed was that during the compression test all cylinders first hit was 80 PSI, then the second hit was 85. It didnt struggle to get there like worn piston rings do.. The wet test only showed 3 PSI improvement. So, Today I did a leakdown test on two cylinders and it had 18% leakdown on a cold engine. Im calling this engine good enough for upgrades..
    So why the lack of Compression pressure ? A late closing exhaust valve due to timing chain wear could cause low compression pressure like another member suggested and that is true..Its also possible that Chev purposely retarded cam timing to reduce compression pressure to help reduce NOX so they wouldn't have to use cat converters to meet emission laws.. This Truck was the last vehicle that passed California emission requirements without a cat converter. This would have caused me some trouble at state inspection time if I was the average guy,,But since Im a state inspector, I knew the laws and it passed every time, well the window tint was iffy.
    So, Im going to continue with the upgrades now that I know the engine is OK. Im not looking at turning it into a race truck, but just something that has slightly lumpy idle that pleases me and a bit more push when I hit the loud pedal..
     
  23. Sharps40

    Sharps40 Price, it's all about the price

    Joined:
    Dec 18, 2016
    Messages:
    1,180
    Likes Received:
    1,632
    Location:
    South Centralish NC.
    I guess I'm confused. You asked about 85 psi. Received much accurate advice about potentially not having a solid foundation and then choose to ignore it perhaps in the mistaken hope that maybe a retarded cam setting is the reason a 35 year old motor has a 30%+ compression pressure deficit.

    I hope it all works great for ya ...
     
    Last edited: May 24, 2020
  24. Lager

    Lager Active Member

    Joined:
    Aug 3, 2017
    Messages:
    602
    Likes Received:
    912
    Location:
    Salisbury NC
    Then please enlighten me as to where my compression pressure went to when the cylinder press test was correct meaning no loss of compression due to cylinder wall, ring wear or valve seating issues? I can only think of one conclusion and thats it the cam design or timing that allowed the exhaust valve to close late resulting in the loss of pressure. I dont think your confused at all, I think you know more then I do. So please educate me in the design of these older engines..
     
  25. Chdamn

    Chdamn Dungeon Master Staff Member Benefactor Charter Life Member

    Joined:
    Dec 16, 2016
    Messages:
    49,943
    Likes Received:
    277,268
    Location:
    In the Dungeon
    230 and 450? Man those are rookie numbers for a 454. You gotta bump those numbers up.
     
    GoWolfpack likes this.
  26. Chdamn

    Chdamn Dungeon Master Staff Member Benefactor Charter Life Member

    Joined:
    Dec 16, 2016
    Messages:
    49,943
    Likes Received:
    277,268
    Location:
    In the Dungeon
    Keep that 454 and check out a company called world products. I used to keep up with them when I had dreams of building a 454.

    They have heads that just by changing them and adjusting your timing you can gain 100 hp and about the same in torque.

    I don’t remember the exact numbers but if you went full retard with their products you could have a 700 or better hp 454 that runs on pump gas.
     
  27. John

    John Member Benefactor Charter Life Member

    Joined:
    Dec 18, 2016
    Messages:
    405
    Likes Received:
    354
    Location:
    Rutherford Co., NC
    I agree the engine is OK for upgrades, to be used for light hauling and towing.
    I would upgrade the cam to a mild towing cam, upgrade the timing set, degree the cam, recurve the distributor, and rebuild the carb. There are people that bush the base plate to take care of the worn shafts. Holleys rule the racetrack, but a Qjet is a fine street carb. I think you will be happy with the results.
     
    confused and Pink_Vapor like this.
  28. LizardKing

    LizardKing Alright Alright Alright Charter Member Supporting Member

    Joined:
    Dec 19, 2016
    Messages:
    1,049
    Likes Received:
    1,304
    Location:
    Charlotte
    I'm in for the carb debate...better'n 9mm vs 45acp!
    FWIW, I replaced my quadrajet (after having it rebuilt) with a Holley, and although I "feel" like the quad made more power, the Holley is definitely more consistent (start up, idle, no lag).

    Like my Dad told me, Horsepower cost money, How fast you wanna go...

    Good luck!
     
    Lager and Button Pusher like this.
  29. Chdamn

    Chdamn Dungeon Master Staff Member Benefactor Charter Life Member

    Joined:
    Dec 16, 2016
    Messages:
    49,943
    Likes Received:
    277,268
    Location:
    In the Dungeon
    My dad was a huge believer in Rochester carbs. But he was a mechanical engineer and could rebuild them and make them do things that Holley never thought about.

    He used to help out a short track race team and made them switch to rochesters.

    Me? I’ve have really good luck with edlebrock 4 barrels. Usually come right out of the box ready to go for whatever application you request.
     
  30. Diablos

    Diablos Senior Member

    Joined:
    Dec 16, 2016
    Messages:
    3,932
    Likes Received:
    14,143
    Location:
    saloon number 10
    This simple mod will wake that big block right up

     
    DirtySCREW, Lager and Button Pusher like this.
  31. Sharps40

    Sharps40 Price, it's all about the price

    Joined:
    Dec 18, 2016
    Messages:
    1,180
    Likes Received:
    1,632
    Location:
    South Centralish NC.
    Most here did already. Your pressure went past the rings or valves on each stroke of the compression test and showed you that your motor can only pump up to 85 psi. No shame, just natural wear.

    A good motor should make 40 psi on the guage on the first stroke and up to 35 psi more each additional stroke of the test until it reaches the limit of what ring seal and valve seal will hold...135+ being very good on average motor. Typically a test should be 6 to 10 compression strokes to get the gauge to show the highest that cylinder can do.

    At 35, look for tired valves and springs, worn cam lobes, sticky lifters , oversize or egg shaped cylinders, scuffed pistons, slack chain, etc. Your 85 psi is not due to a factory retarded cam, rather a well used engine with wear. Consider a professional evaluation if you really dont fully understand why 85 psi is a horribly low compression reading. Your engine made 135 psi or more much of its life until it became worn enough that the seal in the cylinders just wont do that much work any more.
     
    Last edited: May 24, 2020
  32. BowWow

    BowWow Happy to be here

    Joined:
    Jan 6, 2017
    Messages:
    2,803
    Likes Received:
    3,800
    Location:
    NC
    That was normal for the basic workhorse truck engine......but yeah 350+ hp and 550+ torque shouldnt be a big deal.
     
  33. BowWow

    BowWow Happy to be here

    Joined:
    Jan 6, 2017
    Messages:
    2,803
    Likes Received:
    3,800
    Location:
    NC
    Get a service manual and verify your mechanical timing and ignition timing.... If both are OK, 85 psi is low.........
     
    Sharps40 likes this.
  34. Scsmith42

    Scsmith42 Member Benefactor Charter Life Member Supporting Member

    Joined:
    Dec 17, 2016
    Messages:
    1,986
    Likes Received:
    4,228
    Location:
    New Hill, NC
    You're welcome.

    A wet test does not seal the valve seats - only the rings. Your low compression is most likely through the valves; the older 454's had a tendency to wear the valve guides and seats. That would explain the lower compression, along with timing chain slop. I would not be surprised to see significant exhaust valve wear too. 1975 was right around the time that unleaded fuel was coming out, and the early engines did not have the hardened seats / valves issues quite worked out from the loss of the lead lubricant in the fuel.

    Since the wet test indicated only a small improvement in compression, you can probably get by w/o rebuilding the bottom end but you sure should yank the heads and either rebuild them or replace them.

    Quadrajet's are probably one of the most sophisticated street carbs ever made. A good carb guy can do anything with them. By all means have it rebushed and rebuilt; it' will be much more responsive than a Holley.

    Look for a head/intake/cam/carb combo that is designed to work with the factory compression and give you the results that you're looking for. Match the primary tube sizes on the headers with the RPM range that the combo is designed for. Too large a tube and you lose bottom end; too small and it costs you mid and top end. Lower restriction quiet mufflers such as Flowmasters are a good addition too.

    A MSD ignition is a great enhancement to the combo too. As I recall GM was switching over to the HEI distributor right around 1975. Having it recurved will help the mid range too if you don't swap in an aftermarket distributor.
     
  35. Lager

    Lager Active Member

    Joined:
    Aug 3, 2017
    Messages:
    602
    Likes Received:
    912
    Location:
    Salisbury NC
    This build should prove to be interesting and Im just playing around try to show the farm truck some love since Ive neglected it for many years. I dont even know why Im doing this other then Im a bit bored and haven't done any what I call shiny stuff in the past 20 years. Ive been a mechanic for the past 38 years and until 20 years ago I had a great paying side line building race car engines for short track and drag cars. What Im not used to is street cars or trucks and trying to find the proper ratio of components for streetability. If I thought I really needed to do some major work to the lower or upper end of this truck to achieve what I wanted it do? I would have quit even trying because Im too old to be pulling engines and dont have the money since raising 3 grandkids is already sucking up all my money.. I just bought a second or third hand Holley 750 CFM vacuum from a guy for $125. Summit racing had headers for $150, but I wont put them on until the new cam is broke in to save neighbor relations.. Found a Summit cam thats the same as the Edelbrok preformer for just over $100.. Still searching for a cheap used dual plane intake. Some needed gaskets, plus timing chain and gears and I should be done..If it all works out OK, will let you all know.. Im out now..
     
    Trevillian, Button Pusher and ronn47 like this.
  36. LeeMajors

    LeeMajors Newly Empowered Bionic Man Staff Member Charter Member Life Member

    Joined:
    Dec 17, 2016
    Messages:
    3,443
    Likes Received:
    3,750
    Location:
    Lincoln county
    If you have the cash, look in to a gear drive instead of a chain and gears. Degree timing is much easier as well as reliability
     
  37. Mike79

    Mike79 Senior Member

    Joined:
    Dec 16, 2016
    Messages:
    1,262
    Likes Received:
    635
    Location:
    Washington
    Another wrench to toss at you is your 454 is a truck block so make sure you get the correct intake.....as stated several times that 85 psi is low....
    I'm going to say good possibility it's in need of more than a quick timing chain cam lifters and new induction....but I'm also sure not changing the oil and leaving all that acid and water in it hasn't helped you.
    In the end it's your money and also your problem to deal with whatever way you go. I know it is easy for us to say pull it full on rebuild Dmax swap it put EFI on it etc.
    If it's a toy hell why not toss some parts @ it and see how it does....an ignition upgrade is also a cheap investment that would markedly improve things....
     
    Lager likes this.
  38. Pink_Vapor

    Pink_Vapor “Not as funny as he thinks he is”- wife Supporting Member

    Joined:
    Jul 1, 2017
    Messages:
    7,213
    Likes Received:
    9,506
    Location:
    Moncure, NC
    All of what he said, plus a Quad does run great, and usually gets better MPG than a Hollley if you keep your foot out of it, when tuned. @David Hall knows them well.

    A MSD ignition is a great enhancement to the combo too.
     
    Last edited: May 30, 2020
    Scsmith42 likes this.
  39. Sharps40

    Sharps40 Price, it's all about the price

    Joined:
    Dec 18, 2016
    Messages:
    1,180
    Likes Received:
    1,632
    Location:
    South Centralish NC.

    I think with a cam, lifters, chain and a good valve job you'll see compression psi come up. Head work wont break the bank and wont require pulling the motor. It's only another hours work after you pull the intak . Either way post back with pics and details as you progress
     
    Lager likes this.
  40. bondjamesbond

    bondjamesbond Senior Member's Elder Charter Member Supporting Member

    Joined:
    Dec 19, 2016
    Messages:
    12,319
    Likes Received:
    82,105
    Location:
    WNC
    85 psi is low, but you say all cylinders are consistently the same.
    I say not too bad for a 45 year old big block Chevy.
    Jerk it out of the truck and start rebuilding the thing.