[ezobens]

Hello!
I've been enjoying the information on this site for quite some time and have decided to present my ideas for my 400 SBC build up for the board's review and comments.
I currently have a 69' Corvette coupe with a ZZ3 small block, M-20 Muncie and 3.70 axle. This car has no power options- Manual steering, brakes etc.
Being an Oldsmobile big block guy since high school, the torque of the ZZ3 is not quite up to my expectations, so I have the following parts that an would like to put together and toss in the Vette:

1972 400 SBC, 4-bolt main
Bored .040 w/forged L2352F Speed Pro pistons (14cc Dish)
Stock crank and 5.565 rods
L-98 Aluminum heads that have been mildly cleaned up and gasket matched (58cc chambers, 1,94 intake, 1.50 exhaust, LT4 valve springs)
Elgin #E-901-P mechanical 'Duntov 30-30' cam- 254/254 dur @ .050, .485/.485 lift 114 LS.
ZZ4 dual plane aluminum intake with a Holley #4779 straightbore, double pumper carb
Stock distributor (recurved) with Pertronix II module and coil
Z-28 oil pan, windage tray and oil pump

With the pistons and heads, I figure around 10.6 compression-
This is strictly a street car that I'll drive in the summer for fun so valve adjustment etc is not an issue.
I wanted something that sounds cool at the light (hence the 30-30 cam) but gives me a little more kick than the bone stock ZZ3 when the light turns green.

Any comments on if all this will get me to where I am looking or do I have some glaring deficiencies that I need to address?
I realize the cam is a bit wild, but I REALLY love the sound. I figure they ran them in a 327, a 408 shouldn't be too awful?
If it's too hairy, I can always swap it out for something a little milder down the road.

Any clue what kind of power I can expect from this combination?
With a 3200 pound curb weight, 2.52 1st gear and 3.70 axle, will this give me enough low end torque?
Any comments suggestions would be greatly appreciated!
Thank you!
Elm.

[onovakind67]

My CR calculator sees the CR at about 11.3:1, possibly a little high for the application.

[ezobens]

The Speed Pro piston guide gives me 10.55 with a 58cc head?!
I guess I should physically measure all this stuff to see what it yields eh?
Thanks for the info!
Elm.

[454C10]

Those heads aren't very good. Anyway to use something else? Maybe a head with 64cc chambers would be a better choice. If you have the money get a set of 195cc AFR's. Or maybe a set of 200cc dart iron eagles with 72cc combustion chambers for 899.99 from summit racing (would make about 10.5:1 cr with flat tops).

what heads come on a ZZ3?

It is always better to use flat top pistons and adjust the compression ratio with the head combustion chamber volume. If you must use dished pistons use as little of a dish as possible. The flatter the piston, the quicker the flame travel. And faster flame travel require less total ignition timing which allows more compression. Plus with dished pistons you can't take advantage of the quenching effect.

That old cam grind isn't the best choice either. The ramps are very slow and the lift isn't that much. Plus the engine would run better with narrower lobe separation, like 110 degrees. Take a look at the compcam 294S if you want a solid lifter cam.

I run the compcam 292H (hydraulic cam) and that cam is a major fender shaker on my 11:1 cr 362 sbc and doesn't require valve adjustment and the valve train is fairly quiet. It revs to 7200rpm before the valves float.

The ticking from solid lifters get on my nerves. Sounds like an exhaust leak to me.

[drm184]

Originally Posted by ezobens

Hello!
I've been enjoying the information on this site for quite some time and have decided to present my ideas for my 400 SBC build up for the board's review and comments.
I currently have a 69' Corvette coupe with a ZZ3 small block, M-20 Muncie and 3.70 axle. This car has no power options- Manual steering, brakes etc.
Being an Oldsmobile big block guy since high school, the torque of the ZZ3 is not quite up to my expectations, so I have the following parts that an would like to put together and toss in the Vette:

1972 400 SBC, 4-bolt main
Bored .040 w/forged L2352F Speed Pro pistons (14cc Dish)
Stock crank and 5.565 rods
L-98 Aluminum heads that have been mildly cleaned up and gasket matched (58cc chambers, 1,94 intake, 1.50 exhaust, LT4 valve springs)
Elgin #E-901-P mechanical 'Duntov 30-30' cam- 254/254 dur @ .050, .485/.485 lift 114 LS.
ZZ4 dual plane aluminum intake with a Holley #4779 straightbore, double pumper carb
Stock distributor (recurved) with Pertronix II module and coil
Z-28 oil pan, windage tray and oil pump

With the pistons and heads, I figure around 10.6 compression-
This is strictly a street car that I'll drive in the summer for fun so valve adjustment etc is not an issue.
I wanted something that sounds cool at the light (hence the 30-30 cam) but gives me a little more kick than the bone stock ZZ3 when the light turns green.

Any comments on if all this will get me to where I am looking or do I have some glaring deficiencies that I need to address?
I realize the cam is a bit wild, but I REALLY love the sound. I figure they ran them in a 327, a 408 shouldn't be too awful?
If it's too hairy, I can always swap it out for something a little milder down the road.

Any clue what kind of power I can expect from this combination?
With a 3200 pound curb weight, 2.52 1st gear and 3.70 axle, will this give me enough low end torque?
Any comments suggestions would be greatly appreciated!
Thank you!
Elm.

You lucked out and got some good info from the others BUT I`m going in a different direction. If your on a budget, try it this way. FIRST, your heads. If you want to save em, have a machine shop recut for 2:02 / 1:60 valves. You need to feed the cubes and the smaller valves work for smaller 350`s. SECOND, your cam is not wild, by todays standards, it really mild, but since you have the cam try this, 1) change to 1:6 roller rockers. The bump from 1:5 will increase the lift of your cam to about 515, better. 2) If you want more low end scoot get a new timing chain thats adjustable with offset bushings. By installing a 4 deg. advance bushing you will have more low end punch from the same cam. THIRD, your carb is too big for this combo. With bigger heads and roller cam, a 750 is good, BUT if you want a much better throttle response and low end punch drop to a 650. My engine is a 406 with bigger alum. heads and bigger roller cam and I run a 650 race demon and it comes alive off the line and idles far better. FOURTH, your compression is too high for the street. 10:5 should be max. I think Felpro makes a thicker head gasket which will bring the compression down to a better level. Hope this helps, RACE ON, DOUG

[ezobens]

Thank you for the suggestions!
Yes, this is a 'budget' build up- This is why I went with the stock rods, crank and 58cc heads. These are all items I currently have lying around and I got the pistons for next to nothing. Investing another $800+ for another set of heads unfortunately is not in my current budget.
The ZZ3 incidentally also has virtually identical 58cc heads as well.

Since I don't plan on reving much past 5000 (5500 MAX), do I really need to be concerned with going to the larger valves? I realize with the cubes, breathing will be an issue on the top end, but most of my cruising will be below 3500.
The larger intakes only offer a 3% gain (the exhaust would be a little over 9%), would this be that noticeable under 5K or does the move to 1.6 rockers make it more noticeable?

Is the 4 degrees advance on the cam a fairly exacting science (the concept of degreeing and advance/retarding cams has always eluded me) or is this more of a trial and error procedure? Do I need to learn how to 'degree' a cam or can I take the 4 degree figure with a good amount of confidence that it will produce the desired result?

I'll need to cc the heads to get an accurate volume for compression- They are the 58cc L-98 heads that have been ported and polished mildly. The combustion chamber may well be closer to 60cc than 58 these days. With a Fel-Pro #1014 head gasket (.039 thick, 9.2cc I believe), will I be that much over on 'acceptable' compression? What is my limit with 93 octane unleaded?

Thanks again for the tips and advice!

[GoneNova/406]

if you go to chevy high performance magazine.com or super chevy and some of the others you should be able to get a very good idea for a complete build with good tork and power.you have the benefit of their numbers.also i inherited one of the 30-30 cams and have run alot of sims on desk top dyno only to find out that it makes good power up high but never good tork.i was disappointed myself.

[drm184]

Originally Posted by ezobens

Thank you for the suggestions!
Yes, this is a 'budget' build up- This is why I went with the stock rods, crank and 58cc heads. These are all items I currently have lying around and I got the pistons for next to nothing. Investing another $800+ for another set of heads unfortunately is not in my current budget.
The ZZ3 incidentally also has virtually identical 58cc heads as well.

Since I don't plan on reving much past 5000 (5500 MAX), do I really need to be concerned with going to the larger valves? I realize with the cubes, breathing will be an issue on the top end, but most of my cruising will be below 3500.
The larger intakes only offer a 3% gain (the exhaust would be a little over 9%), would this be that noticeable under 5K or does the move to 1.6 rockers make it more noticeable?

Is the 4 degrees advance on the cam a fairly exacting science (the concept of degreeing and advance/retarding cams has always eluded me) or is this more of a trial and error procedure? Do I need to learn how to 'degree' a cam or can I take the 4 degree figure with a good amount of confidence that it will produce the desired result?

I'll need to cc the heads to get an accurate volume for compression- They are the 58cc L-98 heads that have been ported and polished mildly. The combustion chamber may well be closer to 60cc than 58 these days. With a Fel-Pro #1014 head gasket (.039 thick, 9.2cc I believe), will I be that much over on 'acceptable' compression? What is my limit with 93 octane unleaded?

Thanks again for the tips and advice!

When you said that this was going to be a street machine and you are used to low end torque, we can look at it this way. If you are going to limit the RPM, the valves should be O.K. As for compression, general rule is not to exceed 10:5 / 1 on pump gas. The 58cc heads builds compression but the 14cc dish pistons take it down. Go to the tech section of this site for some auto math calcs. that will give you a correct number. If its over 10:5, go with the thicker gaskets. As for the cam, if you advance the cam 4 deg. it will bring the power on 200 to 400 RPM quicker. The adjustable timing gears are easy to install. When you install the new gear, the 4 deg. offset bushing slides in to a precut slot on the gear and your done. The 254 dur. @ .50 and the 114 LS is designed for mid and upper range performance. My 383 is built for low end torque and the dur. @ .50 is 230 and the LS is 108. Advancing your cam will help low end torque. Since you want to keep your valve combo, the 1:5 rockers are O.K., but roller rockers will give you about 10 H.P. gain. The cubes will take the carb but the heads won`t like the 750. Since you have the carb, one trick is to get a 650 base plate which will fit your 750. Too much carb will kill low end. You did not mention the exhaust. With the current heads, don`t go any bigger than 1 5/8" headers and no more than 2 1/2" pipe. Those hyped 3" exhaust that people think are cool will only kill your low end. An X-pipe crossover installed just behind the collectors will help your combo as well. A longer collector will help low end torque. If you have short collectors, add an extention to bring them out to about 28". General rule of thumb is that exhaust back pressure is good for low end and free flow gives it to you on the top end. Torque is good, it what gives you that ear to ear grin when you leave the green lite. DOUG

[coldknock]

The cam you have is large enough to bleed off a good bit of excess cylinder pressure. With 58cc chambers, 0.039" gasket and the pistons 0.025" below deck and a 14cc dish the ratio would be 10.6-1, give or take a few hundredths. The problem is that you'll have a cam designed to work above the rpm you want and also above those heads ability to breathe. It'll work but you'll probably be disappointed.

LW2306F has a 16.2cc d-shaped cup that would bring the ratio down a little with the L98 heads. Try those pistons and heads with 64cc chambers, if that's an option, for a ratio of 9.8-1. With that you can choose a smaller, more modern camshaft that will suit your rpm range. This will also work a lot better with production heads, assuming that's what is within your budget for the engine.

World Products S/R Torquer, and other similar heads, can be found at prices very close to well prepared GM castings. Vortech heads are always an option as well, just make sure you get the valve guide bosses milled to accomodate a cam with more than 0.470" lift and remember that the intakes are more expensive that those for standard SBC heads.


Larry

[deuce4papa]

I'm building an engine that will be very similar to this one. I am using a 5.7" rod. The short 400 rod will cause excessive cylinder wall wear and create a noisy engine, especially with forged pistons. I also have the "fast burn" head with 62 cc chambers to limit the compression ratio. You should have a huge amount of torque to work with. So much so that you can run more cam than you really need, and this extra duration should kill some of the compression by closing the intake later than what would be considered optimum. You will have a good lopey idle and should still have plenty of torque with the small intake runners in those heads and the large cubic inch displacement. I would figure the compression ratio very carefully. Take into consideration the deck height measurement and even the volume between the top of piston and the top ring. Also, adding head gasket thickness may create more pre-ignition problems than it will correct. You may want to work the combustion chambers even more. Hope this helps.

[ezobens]

Thank you all again for the info and advice!

The common thread in everyone's comments seems to be that this isn't the most appropriate cam for my application, in which I would have to agree.
I appreciate your insight and will probably be asking for alternative grind suggestions shortly- Unless you already have some suggestions!
Since I already have this cam, I feel compelled to try it for even a brief period to just get it out of my system. Realistically, if this cam isn't the one for me, I will most likely go back to a flat tappet hydraulic cam anyway.

It also seems that the 750 Holley may be a bit much- I know it was a bit much for the ZZ3 and removed it as soon as I bought the car. I do have a 650 Holley spread bore w/mechanical secondaries that I can use on this motor as well.

I forgot to mention exhaust- I know that I will get a lot of flack for this but I am planning on running the stock factory dual exhaust out to the back bumper. This includes the factory 2" 'Ram Horn' manifolds and 2" pipes all the way back. The only variation is the turbo mufflers in place of the factory units. Will this exhaust configuration be really that bad under 5000 RPM?

Thanks again!
Elm

[454C10]

The problem is you are building high compression and installing a big cam for a high torque and a low rpm application (under 5000 rpm). There is a mismatch in parts going on here. A big cams and high compression is for mid and high rpm operation.

Seems that you have your heads, pistons, and cam already and you don't really want to buy anything else. So, I would do a few things to lower the cylinder pressure a little. Use thicker head gaskets, unshroud the valves all the way to the gaskets to increase combustion chamber volume, and install the cam straight up to delay the intake valve closing point.

Since you have a 3.70 gear and a 4 speed I wouldn't worry too much about torque. A 400 cid sbc with those gears should be quite enough, even with that cam. Plus the 4 speed and 3.70 gears will not load up the engine too much which can make it less likely to detonate.

You need to install ARP rod bolts and plan to spin the motor up to 5500+ rpms. Your 5000 rpm limit is not realistic for that cam and compression.

Wow, those exhaust manifolds will eat up 40 to 50 ftlbs of torque in the mid rpms. Go to chevyhiperformance.com and look in their old tech files. They did a nice header comparison on a 350, and they even tested the stock manifolds. You should at least get a set of Hooker SuperComp block hugger headers. Their performance was right in between the stock manifolds and full length headers and they mount similar to the factory manifolds.

Since you have no quench area with dished pistons, a thicker head gasket will only reduce the likelyhood for detonation. If your engine had quench effect (piston flat part within 0.040" in the flat part of the combustion chamber) then yes, a thicker gasket could make detonation worst.

I have found the opposite when using 5.7 inch rods on a 400. Long rods make a noisy engine due to the very short pistons that are required with 5.7 inch rods and a 400 cid stroke. GM didn't put 5.7 inch rods in the 400 for a reason. The 5.5 rods are a good choice for the street.

You could also sell your L98 heads and pick up a set with more combustion chamber volume.

You do realize that you will need a different balancer and a different flywheel for the 400 (externally balanced). And you need to have steam holes drilled in your cylinder heads.

[ezobens]

Lots to think about here-
The reason I shy away from headers is that I don't want anything hanging lower than the stock exhaust under this car. Since it will be street driven, I have to worry about dragging on things like speed bumps, curbs etc. I'm also a little worried about the heat generated from headers being that close to vintage fiberglass- Just makes me uneasy.
I have seen the 'block hugger' headers and would consider those if I was reasonably sure that I can use the stock exhaust pipes with them (I would have to consider swapping the 2" for 2 1/2" pipes however).

I am a little confused about the comments regarding the compression and that it doesn't help power or torque at low rpm? This doesn't make sense to me- Higher compression will produce more power per cubic inch compared to a lower compression motor of the same size (or so I was led to believe all these years).
How can higher compression hurt low end power? I understand the concern of compression over 10.5 but will a same displacement motor will 9.5CR actually make more power in the low end than the same motor with 10.5CR?

The reason I chose the L-98 heads was with the assumption that compression around 10.5 is more efficient than 9.5- And that aluminum heads are really the only way to get 10.5 and be able to run on pump gas without detonation.
I do realize these heads will need to have the steam holes drilled and I plan on using a 153 tooth steel flywheel that is externally balanced (I don't want to buy a new starter, bell housing and clutch just to accommodate a 168 tooth flywheel).
The balancer is the stock 400 as well but I've heard that going with a 6.75" external balancer is the way to go over the 8"?

I have the original iron 400 heads that came with the motor (76cc) but these seemed to be too far on the other extreme to be of much value for what I was trying to accomplish. With the pistons I have, the 76cc heads would only give me a 8.94CR.
It sounds like my combination will basically work other than my cam and exhaust choices(which are negotiable)- If I can keep the CR under 10.5, I should be OK otherwise?

[454C10]

Yes, more compression does help low rpm torque, but not more compression than pump gas can handle. Mild cams (low rpm torque) build high cylinder pressure (early intake valve closing point) and can't tolerate very high compression ratios on pump gas.

Sure a 12:1 engine with a mild cam and 116 octane fuel will make great torque. But that fuel will get expensive

I'm using a 350 with 11:1 cr, a 292H compcam, 5 spd, 3.90 gear, in a 2600 lb car and it runs will on pump gas. But the engine pulls to over 7000 rpms and doesn't make much torque until 3000 rpms. The light weight of the car, a lot of gears, quenching head/piston set up, and long duration cam make this possible.

Compression should be matched to the cam, and the cam should be matched to the performances desired (low rpm torque, mid range power, or high rpm hp). Your mismatch is that you are building a high compression big cammed engine for a low rpm torque and your not using headers.

9:1 cr isn't bad for a mild cam. Good for a cam about the size of a CompCam 270H, but not enough for the cam you have and want to use. Unfortunately, stock 400 heads will not perform very well with out some porting work.

10.5 cr isn't bad for the cam you have, a little high but not bad. It is just that the cam you have is old school and will not make a bunch of torque, especially with the 114 lobe centers and with very soft ramps (slow valve opening and not very high).

Block huggers with work with the stock pipes. Of course some exhaust work will need to be done to connect them to the pipes. The pipes will not hang down like full length headers. But get the hookers because they have 3/8" flanges and cheaper hugger types uses 1/4" flanges.

I would use the same size balancer that you are using now. Since the pulleys mount to the balancer, a different thickness unit will mess up the belt alignment.

You found a 153 tooth flywheel with a counter weight? What is that off of or is that an aftermarket flywheel?

Yes, your combo will work. But at least install some block huggers and some arp rod bolts for 500 more rpms.

[ezobens]

I really appreciate everyone's patience with my 101 silly questions. You guys are a wealth of information!

The flywheel is a standard 350 153 tooth unit that I was going to use with one of those balance plates they sell for externally balanced 400's. You can buy an aftermarket 153 tooth, externally balanced flywheel as well, but those seem to be pretty pricey. Do you see any issues with using these balance plates between the crank and flywheel?

Back to the cam dilemma- Any suggestions on what would make more sense for my application? Solid or hydraulic is fine- I just want to stay with the flat tappet design for budget reasons. I'd also like to have a bit of a lope at idle, just so I don't sound like a 307 2bbl at the lights. LOL

Thanks again!
Elm.