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#1
11-12-2009, 08:37 AM
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428 Pontiac Engine Question
How good are the 428 engines and did they all have 4 bolt main bearing caps? What to look for when looking at one that is disassembled? Is this a good choice for my 1971 GT-37?
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1971 Pontiac GT-37 Car is a junk yard dog and maybe one day will be restored. 
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#2
11-12-2009, 09:38 AM
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428s are among the best basis for a performance Pontiac. No, not all were 4-bolts, but that doesn't make any difference until power levels exceed 650 HP.
Pontiac blocks are known to crack in the main webs from stress and in the valley from freezing. Have the block thermally cleaned and magnefluxed. Jim |
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#3
11-12-2009, 10:13 AM
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There were also some 428 block that came drilled for 4 bolts but had 2 bolt caps from the factory. They can be upgraded with 4 bolk caps and line bored.
Check your motor mount pattern in your car as all 428 blocks are set up to take the 2 bolt mount (located further back) not a 3 bolt mount. There are conversion kits available. |
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#4
11-12-2009, 10:19 AM
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428's /Pontiac Gregg
1967 and 68 428's were all 4 bolt mains The 1969's may or may not be 4 bolt.
The 428 is my favorite motor, love the bore to stroke ratio. Now you put a 428 crank in a 40 over 455= 441 c.i what a screamer !! With good AMERICAN forged rods, solid lifter cam, I take them to 7400 r.p.m. Assuming the heads are ported correctly. I have better 1/2 's 434 c.i. motor set up with a 8400 rav. chip. Pontiac Gregg
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Greg Merrick |
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#5
11-18-2009, 08:37 AM
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Just picked up a 428 4 bolt main last night that was diassembled. Recently was bored .040 over. Missing the front timing cover, cam, intake. Has #62 heads that had hardened valve seats installed. Has a standard crank. Do I need any special front timing cover and balancer? The engine also came with a set of rods he claimed were like the 421 SD rods. They were shot peened and resized and have ARP bolts on them. Has the .040 pistons too. Even has some sort of windage tray that goes in the bottom end and some oil deflectors that go above the rockers. I never seen these before. Anything I else I should know?
__________________
1971 Pontiac GT-37 Car is a junk yard dog and maybe one day will be restored.
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#6
11-18-2009, 10:15 AM
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SD rods are 2" from "pad to pad" (where the bolt head sits and the nut "seats"). "Rubber rods" are 1 15/16".
All 428s had windage trays. Look closely for cracks before using. Timing cover, water pump and balancer fit from most Pontiac engines. Year-specific may require "matched" parts. Pulleys can be a real bag of worms. An increase in the size of the "dish" (428 pistons have a 2" or so dish in the center) is required to make the 62s "pump gas friendly". A .060 over 428 is a "440", and perhaps the BEST combination of factory pieces for racing. Jim |
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#7
11-18-2009, 12:28 PM
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Quote:
Thanks. Where should I be looking for cracks? What do you think the compression ratio is on this 428 with the #62 heads?
__________________
1971 Pontiac GT-37 Car is a junk yard dog and maybe one day will be restored.
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#8
11-18-2009, 01:09 PM
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The true SD rods unlike the 58-62 production rods have a very clearly stamped GM in the I beam, the others are barly raised and spotty.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#9
11-18-2009, 03:14 PM
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Cracks appear in the valley and the main bulkheads. Some are on the outside. These are usually from freezing water left inside. Same with the valley. The bulkheads will crack from stress.
Advertised with 62s was 10.5 or 10.75, a numbers guy can tell you for sure. Generally, ACTUAL compression is in the 10:1 range. Jim |
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#10
11-19-2009, 08:34 AM
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Quote:
__________________
1971 Pontiac GT-37 Car is a junk yard dog and maybe one day will be restored.
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#11
11-19-2009, 11:00 AM
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What engine is in you car now? 350? You should be able to use the timing chain cover, and all the brackets, water pump (new), and pulleys from that motor. The key is to find a matched set up. There is a different length water pump on the 68 or 69 motors, its shorter.
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#12
11-19-2009, 12:37 PM
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Quote:
__________________
1971 Pontiac GT-37 Car is a junk yard dog and maybe one day will be restored.
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#13
11-20-2009, 12:42 PM
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The pistons have what appears to be a small dome about 2" long and 1" wide and 1/" tall. Does that sound right for a 428? The rods do measure about 2" from the top and bottom cap where the rod bolt goes.
__________________
1971 Pontiac GT-37 Car is a junk yard dog and maybe one day will be restored.
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#14
11-20-2009, 09:32 PM
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No it should look like the one in the pic. This one is a .040 over 428 TRW forged piston. But that's what it should look like. It should have a flat top with about a 2" diameter circle dish in the middle which lowers the compression a tad.
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Come take a ride http://www.youtube.com/watch?v=P7Y8Awfk2I0 2008, 2013, 2015, 2016, 2019 Central Il Dragway Mod track champion and 2015 IHRA Div 5 Mod champion 
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#15
11-21-2009, 01:11 AM
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Quote:
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Bill 64 GTO, tube chassis w/606" IA tall deck, PG & a pro geared Fab 9". 2750 lbs. 8.2550@164.17-1/4, 5.2901@131.97-1/8, 1.1981-60-ft. 8/10/08 
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#16
11-22-2009, 08:55 PM
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Quote:
__________________
1971 Pontiac GT-37 Car is a junk yard dog and maybe one day will be restored.
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#17
11-22-2009, 08:57 PM
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Quote:
__________________
1971 Pontiac GT-37 Car is a junk yard dog and maybe one day will be restored.
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#18
11-24-2009, 08:27 AM
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Here are a couple pictures of the 428.
The pistons do not appear to be dished at all except where they are relieved for the valves.       
__________________
1971 Pontiac GT-37 Car is a junk yard dog and maybe one day will be restored.
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#19
11-24-2009, 11:53 AM
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The rod you show is a stock cast rod,the pistons will probably yeild 11.5:1 or more compression with 62 heads and the XF block is a good thick block.
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#20
11-24-2009, 02:26 PM
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The rods are cast and the pistons look like old pop up forgings. Whatever the case they do not look stock.
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