Well phooey - Blew up my 383. I was running Z-28 GM steel rods and broke two of them. One rod and piston went through the block just above the pan rail, another acted like a pinball all over the inside of the motor. Never found the loose one, I guess it went down and hit the pavement someplace. With this motor/ short block gone (heads seem to be OK), I'm going to build a 400. I have a "511" two bolt block (a 1970-73 GM Replacement block).

Couple of questions -

With the ProTopLine Heads I have (200cc intake runners x 1.05i x 1.60e and 64cc chambers), and either a Comp Cam 288 Extreme, or Comp Cam X274R (Undecided here because of lots of weekend street driving), will it be Ok in the 406 to be running 10.5:1 compression, with the pump gas we have. My old 383 was not forged bottom and was at 9.8:1, which was great with hi-test gas. This new 400 will be all forged short block this time.

Last time I was running high compression (at 13:1) was 1973, when ethyl was 105 octane leaded. Great gas in those days .

Second question - I have a Bowtie Phase 1 700R4with a 10" 2800/3000 stall Converter...If I reach 450hp or so with the 400 sbc, will the 700R4 phase 1 hold it (Maybe I should contact Bowtie Overdrive on this - they could probably re-do it if not).

Any way, I'm concerned about the compression being bumped up to 10.5:1. 0r should I hold it to something lower for street ability?

Plans are for a Scatt Forged 400 crank at 3.75" Internal Bal, 5.7" 4340 H beam float rods, And Speed Pro coated Hypers - With all of this and with the ProTopLine Heads the compression figures out to 10.5:1 (with block decked at "0", .030 over, and MR. Gasket p/n 5801).

What does every one think? Is 10.5:1 to much for the street, pump gas, aluminum heads, and cam duration? Thanks for all, Cocacolakidd.

 

Yeah, probably be okay. As long as you run premium. Be prepared to take some timing out of it though.

Sorry to hear about your 383. Was there any warning? Any rattling or knocking before it blew? How was it being driven at the moment it let go?

Reason I ask is because with the long stroke and not-great rod/stroke ratio, there is a physical limit to rpms because of the critical piston speed when metal fatigue rips a rod in half.

You'd run into the same thing in the 400 unless you go forged or soften your driving habits which is probably not likely. So going forged would be good. You might want to observe about a 6000 rpm limit, maybe 6500 at the most momentarily.

 

Really dumb on my part...I was going over to the coast (I live in Oregon, and lots of big mountains here) on a twisty, windy, up and down road. I was showing off, and at high revs slipped past 2nd to neutral (without rev limiter) is when it let go. Lots of smoke, noise and shook all over - to the side of the road. It was still running when I shut it off - Probably would not have ran much farther, so I was quick to shut it off. Of course it will not re-start now. The inside of the block looks like a war zone at Phu Bie (spring of 68).

The new motor (electronics) will have a rev limiter set to 6000 or 6500 as you suggested. I now wish I would have had one set before. Such is life - the 383 was not the most expensive build, but it ran good and strong. I have this "511" 2 bolt block ready to go (been sitting wrapped for over a year). It's .030" over, and decked to 9.00" (needed this to clean it up). Splayed 18* 4 bolt caps, drilled oil passages, extra flashing removed, etc., etc.

So the question was to keep the same ProTopLine Heads (their OK), which puts the new build in at 10.5:1 - Or go with new heads at 76cc. This will drop the comp. ratio down to 9.7:1 or so. This is very streetable ratio with premium gas.

While I'm here, is any one familiar with "Canton" Oil Pans? They make one for road racing - that has extra oil capacity without the deep sump (I'm lowered, so ground clearance is a problem)...Are they good quality???

 

Sounds like you have a nice setup planed out already. I'd keep the 64cc heads and lower the compression with different pistons. Ive played with dished pistons a couple years ago, I guess people are starting to figure out they have better flame travel then flat top pistons as long as the compression is descent you will be good. No point in having a high compression engine, not being able to get gas for it and lowering the timing to the point where you loose power.

The 700R you have might not be able to hold up with this new build, from what Ive read on the builders site it's borderline. I'd talk to the builder and see what they suggest.

Good luck with the new engine!

 

Good suggestion - Hadn't thought about that. Dished pistons would be the best way to go. Maybe even better than flat tops. I hate to push the envelope on compression with a weekend/cruse street machine. Should run like a scared rabbit even at 9.5:1 comp.

Thanks again, cocacolakidd.

 

I would highly reccomend keeping it at 10.5:1 with alumie heads for the sake of heat lose in the chamber. I'm at 11.3:1 and run 92-92 octane all say long. 36* total timing all in by 3500rpm. specs of cam are in sig. I for one am more than happy with the streetability of my motor, I installed a vacuum canister in line just in case I did'nt pull enough vacumm and I have no problem running my power brakes, I'll be a hard sell to ever have manual brakes as I have not driven a single vehicle yet in many different forms of brake systems that match the extreme stopping power with minimal effort the power brakes offer.

There's really not much power to be gained by running high compression as what is commonly thought. Reasoning for running the diesel like compression ratios is baised for race type cams with huge duration and cylinder bleeding. I race every weekend and am very competative so I personally make it a point to run valves the day before every race to make sure everything's in check for consistency so I can utilize my log book to try andhelp figure out dials. The times where I took the scheduled weekend off (Mon-Fri I street drive the living heck outta this thing) the valves were still right on the money. If you go solid roller just be sure to buy the best roller lifters you can afford as well as the best valves springs as these are the KEY elements for keeping everything together with no problems.

10.5:1+aluminum heads+right duration cam+92/93 octane=no problems and lotsa smiles

 

cocacolakidd - Your story sounds almost identical to mine. I had a 383 in my 86 TA. I was taking it out for one last cruise before putting it away for the winter. While winding out 2nd gear, a rod let loose and went through the side of the block.

I replaced the 383 with a 400. I decided to use the cast crank but upgrade the rods to 6" Eagle rods and SRP flattop pistons. I had the motor zero decked so I could achieve a near perfect .040" quench. The quench is a very important factor in controlling detonation. I'm using Brodix RR200 heads that have 68cc chambers and .040" head gasket. My compression is right at
11.0-1 and I run pump gas. For cam, I have a Comp XE solid roller 242/242 .603 lift on a 112 lsa.

This combination is working well. The motor feels very strong(no et or hp numbers) and it passed an Ohio E-Check. Keep in mind though that I am fuel injected.

Good luck!

www.geocities.com/dzperf

 

you were running 13:1 on 105 fuel in 73, when you were 8 years old?

 

I take it you missed the story in the news of the 4yr old that took his moms car to his freinds house. Started it up, drove it 1/4mi. away, found out freind was'nt home so got back in and drove home. Cop noticed car going really slow and weaving so followed it back to the kids apartment complex where it ran into a parked car in the parking lot, kid put it in reverse and backed into the cop car.

Musta been an older car since the brake did'nt need to be depressed to engage a gear and idle musta been kinda high to idle the car down the road in gear. The mother had no idea that had taken place.....so...4 more years expereince and it's entirely plausible he wa running a 13:1 on 105 when he was 8yrs old Plauisble but not likely

 

Hummm...Sorry something is amiss here. Let's figure it out. Birth date of December 1945 puts me at 28yo in 73 - Plenty of experience to be driving. Yeah I'm an old fart going through a second child hood with fast cars...Well I have had fast cars all along. So maybe it's a mid-life crisis to still like, and want a sleek and fast Third Gen. Between the Porches and Vetts and Chevys there has always been a Camaro since 1970. Sorry - Where did you think I was only a tot in 73.

That tot driving story is like the one just in the news of the 8yo driving. He was driving so erratically a cop was to pull him over because the car was all over the road. It seems he had to jump down to hit the gas, and then jump back up to see where he was going, and steer. It seems as he snuck out after midnight with his mom and dad's car.

 

It must have been my profile...I just checked it, and there was a DOB of 65...it was wrong, It is correct now (a couple of other things were amiss also - corrected). Sorry for the wrong info in the profile. Cocacolakidd -

 

fat fingered the keys, 20 years makes a big differance.