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post #1 of 14 (permalink) Old 07-06-2016, 07:34 PM Thread Starter
 
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400 Rebuild Advice

Hello guys,

What should I look for in shop that will do the fresh bore, suggestions, do and doníts, weak points that should be addressed to avoid engine failure, things i should greatly consider doing in this process? Any help, advice, expertise, or insults are greatly welcomed!

More info/backstory:

Block is a 400 from a 1970 Bonneville, 1970-16 heads (small valve I believe) Intake manifold is from 1975. My friend and I were in the process of getting the car on the road, when come to find out lifters were bad and had a bent pushrod. We tore the block down and inspected everything, which looked to be in good shape. Cylinder walls look to be in good shape as well. I purchased a re-ring/seal kit from summit as I was under the impression everything was good to go, just needed to clean the sludgey nasty up, and purchased a new cam, lifters, and pushrods and paint it back to blue. Once, we got ready to begin reassembly, we found #1 and #7 piston heads had cracks where the rings went.

I have been all over forums and such and reading about flat top pistons, CR, heads, crap pump gas causing detonation, cams, etcÖ This is my first Rodeo and I have literally read myself into a cold sweat and lack of sleep, because I donít really understand how to tie it all together and create a reliable power plant. My friend who is graciously helping me with everything, has built some fine examples of high HP Ford motors in the past, and itís not that I do not trust his judgment. Actually, I feel like a 4 year old that has just too many questions.

He suggested having the block bored over .030, since we need to purchase new piston heads anyways, and with a fresh bore it will be an extra piece of mind, give me a bump in power without rendering everything I have already done obsolete, and allow me the confidence that itís not going to go boom one day (as long as I donít abuse it). I only ever planned to run 93 octane. I have a brand new summit cam with duration 288/298, Lift .444/.466, and honestly everything is newly rebuilt or brand new, minus block/pistons/crank/heads.

Iím already hemorrhaging $$ on this car, as I like to do things the right way and because I was bamboozled by the family member I bought it from (weeeee!). My plan for the car is just a fun street cruiser for a while that can tear the tires up. Originally, i wanted an 11ís street car, but thatís far down the road now, and Iím just concerned with actually being able to drive it before judgment day.

Thanks for any help!
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post #2 of 14 (permalink) Old 07-06-2016, 08:37 PM
 
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Here's sorta what I'd shoot for, but with the addition of the RPM 5140 forged rods.

400 Long Block

SAE 5140 STOCK ROD


"...He suggested having the block bored over .030, since we need to purchase new piston heads anyways..."

Here's the SP forged pistons with Moly rings.

http://www.ebay.com/itm/Speed-Pro-TR...RWvhp2&vxp=mtr


"...1970-16 heads (small valve I believe)..."

Looks like these heads had 78cc chambers.

http://www.classicpontiac.org/FAQ.asp?myPage=V8HeadInfo

If they'll clean up at 78cc, you can build a 406 with just over 9.6 compression.

http://www.wallaceracing.com/cr_test2.php

But, those heads have press-in studs. Since your cam has more than stock lift, with fresh matching springs, it is possible that you could pull a stud. But, maybe not. Some have got by with press studs and a bigger cam than yours. Having the heads changed over to screw-in studs will probably cost around $200. Rather than do that, I'd prefer to buy some 6x-4 heads. They have screw-in studs, 2.11 intake valves, and factory hardened valve seats.

Last edited by oldskool; 07-06-2016 at 09:14 PM.
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post #3 of 14 (permalink) Old 07-06-2016, 09:20 PM
 
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Not trying to earmark this thread, but in addition to the above, can a pontiac 350 be bored to 400? based on my understanding, the only difference between the 350 and 400 is bore...rods, heads, etc. all the same. Am I correct?

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post #4 of 14 (permalink) Old 07-07-2016, 07:13 AM
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Great advice on the forged rods and screw-in studs.
Your profile doesn't indicate what part of the country you're in so I'm not sure who to recommend to you. There are a few good Pontiac builders out there. I've got one of those "11 second street cars" myself and I built it all myself, so I know a little about what it takes to get there. A big part of it is thinking about the whole car, not just the engine, as all the various systems affect each other.

And to answer xcmac26's question: Yes, the only difference between a 350 and a 400 is bore size, but no, it's not possible to bore a 350 out to a 400. The reason is that you'd have to bore the 350 by +.245 over stock (4.12 in a 400 vs 3.875 in a 350) which is WAY past the practical limit of +0.060. However, you could stroke the 350 by using a 4.250 stroker crank (stock is 3.750, just like 400) and get to from 400 (std bore) to 413 (+0.060 over bore) inches. In theory at least. Finding pistons to fit both in terms of the needed bore size and piston pin height might require having very expensive custom pistons made. Cylinder heads could be a problem too. Running 400 (or 428-455) heads with large valves on a 350 block is probably going to require notching the tops of the cylinders to provide clearance for the valves, and even then having the valves that close to the cylinder walls is going to affect flow, and therefore performance.

Bear

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post #5 of 14 (permalink) Old 07-07-2016, 09:51 AM
 
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You mentioned reading tons of stuff on the forums but didn't mention books.

Two of the best books for doing up one's first Pontiac engone are the books by Rocky Rotella. He posts alot on the PY forum and the Firebird ones but his advice is sound, and his books read well and have tons of color photos. Here they are:

https://www.amazon.com/How-Rebuild-P...=rocky+rotella

https://www.amazon.com/Build-Max-Per...=rocky+rotella

(On one of Bear's posts is a great photo of him with Rocky.)

If you don't have these, get them. Rocky walks you through a performance rebuild on a 400 and tells you what you need and don't.
Best of luck to you!
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post #6 of 14 (permalink) Old 07-07-2016, 11:29 AM
 
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"...you could stroke the 350 by using a 4.250 stroker crank..."


Yeah, Butler shows both a 4" & 4.25" 350 block stroker assembly.

Butler Performance - Pontiac Engine & Rotating Assembly Combinations - Featuring Eagle Pontiac Kits

Ace Brewer use to build some pretty nice 383's.

Small-Bore Pontiac Performance Engine Build - Revenge Of The 350

I bought a '69 Tempest which had been built as an NHRA Stocker, with a 350HO engine. It also came with the dyno sheets. It made 434hp.

Here's a Believe it or not--like him or not article.

http://www.hotrod.com/how-to/engine/672hp-pontiac-350s/

Last edited by oldskool; 07-07-2016 at 11:45 AM.
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post #7 of 14 (permalink) Old 07-07-2016, 12:02 PM Thread Starter
 
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Originally Posted by oldskool View Post
Here's sorta what I'd shoot for, but with the addition of the RPM 5140 forged rods.

400 Long Block

SAE 5140 STOCK ROD


"...He suggested having the block bored over .030, since we need to purchase new piston heads anyways..."

Here's the SP forged pistons with Moly rings.

Speed Pro TRW Pontiac 400 Forged Coated Skirt Flat Top Pistons Moly Rings 30 | eBay


"...1970-16 heads (small valve I believe)..."

Looks like these heads had 78cc chambers.

Alamo Area Chapter of the Pontiac-Oakland Club International (AACPOCI)

If they'll clean up at 78cc, you can build a 406 with just over 9.6 compression.

Compression Ratio Calculator - Wallace Racing

But, those heads have press-in studs. Since your cam has more than stock lift, with fresh matching springs, it is possible that you could pull a stud. But, maybe not. Some have got by with press studs and a bigger cam than yours. Having the heads changed over to screw-in studs will probably cost around $200. Rather than do that, I'd prefer to buy some 6x-4 heads. They have screw-in studs, 2.11 intake valves, and factory hardened valve seats.
Thank you sir!

That long block is what i was thinking about purchasing from the get go, but i initially found and thought everything was ok just needed to be cleaned. Engage Murphy's Law lol. I think i will try to get away with the 16 heads i have for now, and go ahead and do the forged rods and pistons. I have read back and forth arguments regarding the cast rods and pistons, and was looking at a set of 8 cast piston heads from sealed pro. But, i guess what's a couple dollars difference, if i'm not going to shoot a rod through the oil pan or block. I've read that the crank is for the most part pretty stout, so long as you're not rev'ing to stupid digits?

Last edited by CptTheAlex; 07-07-2016 at 12:15 PM.
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post #8 of 14 (permalink) Old 07-07-2016, 12:13 PM Thread Starter
 
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Originally Posted by xcmac26 View Post
Not trying to earmark this thread, but in addition to the above, can a pontiac 350 be bored to 400? based on my understanding, the only difference between the 350 and 400 is bore...rods, heads, etc. all the same. Am I correct?
All good man!

Quote:
Originally Posted by BearGFR View Post
Great advice on the forged rods and screw-in studs.
Your profile doesn't indicate what part of the country you're in so I'm not sure who to recommend to you. There are a few good Pontiac builders out there. I've got one of those "11 second street cars" myself and I built it all myself, so I know a little about what it takes to get there. A big part of it is thinking about the whole car, not just the engine, as all the various systems affect each other.

Bear
Located in Greensboro North Carolina, about 3 hours from CVMS, which i had considered, but was trying to avoid having to find another 4-6 grand for a new motor, that might make the trans obsolete.

List: Trans is a freshly rebuilt TH350, was built to handle up to 500, or at least that's what i requested. Rear end is a 2.93, which was just drained and cleaned out. Fuel system is all brand new, in the process of installing the right stuff disc conversion kit, replacing all the brake lines. Car is a post car and has a brand new G-force crossmember. Champion radiator 3-core. New bilsteins, all 4. Upgraded from points to DUI-HEI dist. Original Q-jet was jsut rebuilt and has been run for maybe all of 20 mins. Brand new mini-starter from summit. So, quite literally, down to just the engine being the only achilles heel..

Quote:
Originally Posted by 1968gto421 View Post
You mentioned reading tons of stuff on the forums but didn't mention books.

Two of the best books for doing up one's first Pontiac engone are the books by Rocky Rotella. He posts alot on the PY forum and the Firebird ones but his advice is sound, and his books read well and have tons of color photos. Here they are:

https://www.amazon.com/How-Rebuild-P...=rocky+rotella

https://www.amazon.com/Build-Max-Per...=rocky+rotella

(On one of Bear's posts is a great photo of him with Rocky.)

If you don't have these, get them. Rocky walks you through a performance rebuild on a 400 and tells you what you need and don't.
Best of luck to you!
Thank you sir! I went ahead and purchased the first one, since i'm not sure a Max performance build is in the budget right now. I had been putting off buying the book because i was reading mixed reviews about it being "dated".
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post #9 of 14 (permalink) Old 07-07-2016, 04:48 PM
 
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"...was looking at a set of 8 cast piston heads from sealed pro..."


Those 400 cast pistons are the dreaded "8-eyebrow" pistons. They have 8 valve reliefs and a bevel around the edge of the top. They sit lower in the cyl than the forged units, and will decrease the compression and increase the quench distance. They have lots of sharp edges, and are said to be detonation prone.

Nobody who knows Pontiacs recommends them.

https://www.summitracing.com/parts/s...w/make/pontiac


"...about 3 hours from CVMS, which i had considered..."

Probably not a good idea, at this time.

https://www.gtoforum.com/f170/central...review-106018/
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post #10 of 14 (permalink) Old 07-07-2016, 05:19 PM Thread Starter
 
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Originally Posted by oldskool View Post
"...was looking at a set of 8 cast piston heads from sealed pro..."


Those 400 cast pistons are the dreaded "8-eyebrow" pistons. They have 8 valve reliefs and a bevel around the edge of the top. They sit lower in the cyl than the forged units, and will decrease the compression and increase the quench distance. They have lots of sharp edges, and are said to be detonation prone.

Nobody who knows Pontiacs recommends them.

https://www.summitracing.com/parts/s...w/make/pontiac


"...about 3 hours from CVMS, which i had considered..."

Probably not a good idea, at this time.

https://www.gtoforum.com/f170/central...review-106018/
Yeah, i think i'm just going to follow your advice, and links. (lol) Already spent all this money as is, whats another grand LOL. Whats the point in asking, if i ignore it and do what i want...

I literally read that post from Goat Roper, after i replied about CVMS... Jaw hit the ground...

I found a race shop near me, they have quite a few SBC race engines, going to see what they can do for me on a Pontiac as far as machining. Told me 10-15 for the wrist pins ea. , and 150 to bore out the block to .030.

Unless of course Bear or anyone else knows someone with in reasonable distance that does good Pontiac work. I'd go to Butler, but it's an 8 hour haul for me.
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