[drevil1]

I could use some help with a new engine that I recently bought from another member here. It's a 73' 20 over 400. Stock crank and rods, balanced and assembled. It has stock 87cc edelbrock heads/arp bolts. Installed is a comp 280ah-10 flat tappet hyd.The motor is fully assembled and complete ready to install. I am putting it in a 69 gto conv.It has 3.55 gears, th400/2200 stall, and I plan on using my rpm intake and holly street avenger 770 carb. Of course I just recently bought d port headers,figures.My main concern is the cam, which is comps RA IV. I don't take the car to the track, or race it. But I do drive it HARD. I currently have the Crower 60916 cam in the original engine,with rpm and holly on top,acell electronic dist and headers into 2 1/2 exhaust.I like the "personality" of the engine as it is but would like more "freight train" since I now have the e-heads. I would consider the crower cam pretty tame but decent.

So basically what I am asking is what would be a better choice of cam for this combo, than the comp cam already installed.I was originally going to just throw it in and run what was in it , just to see. But I don't think I have enough stall, or gears, and I would prefer a broad flat torque curve as opposed to a high rpm race engine. I don't want to go too big and lose my lower rpm power, and I'm afraid of leaving too much on the table and not using the potential of the heads.

Also what headers, or RA manifolds would be best. I have only been able to find 2 headers for round port . Dougs, and Hooker super comps. Is that all there is ?
Oh the pistons are flat tops, forged. I was told this motor was built to be about 9-9.5 to 1 compression.
Her is a link to the ad from which I bought the motor. Paul the seller is a great guy and was very helpful when I went to pick up the engine. http://forums.maxperformanceinc.com/...d.php?t=615687

Thanks in advance , and sorry for such a long post.

A pic of the cam card for the cam in the motor .

[vtxman]

On the surface, the biggest problem with your combo is your compression ratio. Typically the 87cc heads are used for a 455 or larger engine. Here is a calculator you can use to determine the compression ratio.

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

This is what I came up with:

Your displacement is 404.04 CID
The Compression Ratio is: 8.86

For an aluminum headed engine, I would want closer to 10 or 10.5-1 compression ratio. The RA IV cam would be a great choice if you had more compression. With what you have, you would have very little lower rpm power. I would choose the Crower cam if you were to run the lower compression.

I see two other options. First is to obtain a cylinder head with 72cc chambers. The second is to obtain a stroker crank. (4.21 stroke) Either of these options will get you to 10:1 compression and then the Comp Cam would be a great choice.

JMO

[drevil1]

Originally Posted by vtxman

On the surface, the biggest problem with your combo is your compression ratio. Typically the 87cc heads are used for a 455 or larger engine. Here is a calculator you can use to determine the compression ratio.

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

This is what I came up with:

Your displacement is 404.04 CID
The Compression Ratio is: 8.86

I went to wallerracing and ran the calculator. It's very easy to manipulate the end result just by changing gasket thickness, deck height, and other options. It's very possible the cr is 9-1 as I was told. Assuming 9-1 cr ,do you think that crower cam is the best choice for a 400 with e-heads? I thought that crower cam, the 60916, needed closer to 10-1 cr. I also have a comp cams xe268, but thought it would be too small.Is 9-1 cr too low for aluminum heads?
Thanks again.

[Cliff R]

Unless the engine is zero decked with two valve relief pistons and thin head gasket, it's probably down around 8.5-8.8 to 1 compression, could be even lower than that.

In an case, the 87 cc heads are not the "hot" ticket for the 400 right to start with. Huge runners, big cam, and low compression aren't going to produce a 1hp/cid engine with tons of low end and mid-range power.

You need at least 10 to 1, near 11 to 1 would be better, to effectively use the RAIV size camshafts. The problem with using smaller cams with the lower compression ratio, is that you are not utilizing the potential of the big runner Edelbrock heads.

+1 for the previous post. A 4.21 or 4.25" stroker kit would be the best option, IMHO. This would cover the compression ratio deal, and allow you to effectively use the cam you have already chosen......Cliff

[drevil1]

UHGG!! I only bought this motor because it was machined and assembled ,done. Fwiw I didnt choose the raIV cam, it came in the motor as I got it. I guess I need to pull a head off and see where the deck is, and what head gaskets are on there. I will attempt to cc the heads also, maybe they were cut? I hadnt really thought about the cr being too low, just going on what I was told. I thought I could just find a better cam for my application. I will report back with my findings. Thanks, Joe

[Cliff R]

The RAIV sized cam requires at least 10 to 1, 11 to 1 would be better, in the 400 engine. The engine will be a real "turd" if you don't raise the compression ratio, and/or install a smaller cam.

Put it this way, my engine in the signature below, uses 76 cc aluminum heads, flat top JE pistons with 2 valve reliefs, and a 236/245/112 camshaft. It also has 455 cid, right at 11 to 1 compression ratio, and I wouldn't even consider less compression for that particular combination of parts.......Cliff

[Evil Stu]

DrEvil,

Another viable option would be to find the 72cc E-heads. They'll bump your CR up to 10+:1 on a 400. Lots of guys doing 455/stoker based combos would buy your 87cc heads. You may still want a cam change but that's much easier than pulling apart your bottom end for a crank swap.

Stu

Edit: I see vtxman already said that.

[Cliff R]

Good advise Stu, and probably the best route to go considering the situation......Cliff

[drevil1]

Just got home from work, having a cup of coffee then out to the garage. I will let you know what Ive got.
I would definately swap heads with someone before taking the motor apart. Picture me a month ago explaining to my wife how this motorwas what I needed, and now telling her I have to buy a crank and rods while Im in there. She'll kill me in my sleep.

[vtxman]

Originally Posted by drevil1

Picture me a month ago explaining to my wife how this motorwas what I needed, and now telling her I have to buy a crank and rods while Im in there. She'll kill me in my sleep.

I can totally relate. You may need to practice sleeping with one eye open........either that, or get real good at hiding parts in the garage where she won't find them. But then again, she will probably see the credit card bill. What to do......isn't this fun!

Good luck with your build!

[drevil1]

Here's what I found.
1: Pistons are TRW L2262F .030 not .020 like I thought. 4 valve relief 6.7cc
2: FelPro 1016 head gasket .039
3: Block decked to .010 - .012
4: Heads dont appear to be milled, but I really don't know. I took some pics if anyone can tell from the surface or from the comb. chambers. I need a more accurate measuring cup, mine showed almost 100 ml to fill a chamber. That can't be right.

Conclusion with 87cc heads and the #s above I get 8.96 cr.

If I change the head gasket to a .035 thick, I get 9.03 cr.

If I changed heads to 72cc edelbrocks with .039 gasket, I get 10.29 cr.

Is there really that much of a difference from the 9-1 cr to 10.29-1 cr ?

Let me ask this way; Can the new motor with 87cc e-heads at 9-1cr ,have more power/torque than my existing motor, iron head 10-1 cr ,60916 cam ?
Thats what I'm after. If it can't be done at 9-1 cr, I will look to trade heads.

At least I have the whole winter ahead of me. Thanks again.

[HWYSTR455]

What kind of iron heads do you have? What's the condition of the engine you have in the car now? Is the '72 block a thick web block? (most likely) How about the one in the car now?

You could run the engine the way it is now, it would run good, and make good power. It's not optimum, but not terrible by any stretch. You will probably be surprised at how much timing it wants!

The heads are fresh, and would be easiest to barter or trade for 72s, BUT, you may want to hang on to them if you plan on doing a stroker in the future.

You could freshen up the iron heads and throw them on the fresh short block, drive it, and do a long-term stroker build on what you pull out of the car. And in that combo, you could choose just about any cam and target any characteristics you want. You could open the ring gaps a touch and spray the heck out of it! Heh-heh! (don't let anyone shy you away of making power because of the rods either).

You have an engine for the rotation now! Heh-heh!

.

[mechanic17]

So throw it back together with the xe268 and burn rubber. I don't think you need to use the rhoads with that one, so save 'em for the RAiv when it goes in something else. I ran a 400 at 8.0 to 1 for a few years on the street and it was still strong.

[HWYSTR455]

Ah, original engine, understand why you don't want it in the rotation. Yeah, as I mentioned, and others too, it's not an optimum combo, but you should be fine with it. I'm a Crower fan, obvious from other posts, so I would lean towards the 60916. I would say though that you would be best off purchasing a new cam and lifters, but that's your call. And considering the type of build the engine is, I would stick with a hyd cam, save the roller money for another build.


.

[Slick]

drevil1,

Given that you're trying to use what you have and minimize further out of pocket expenses right not, the best advice, already mentioned, may be to rebuild those 62 heads. Compression will be right on for the RAIV cam.

IF money permits, I'm sure you'd be pleased with the results of a port job on them by someone like SD Performance. But that may be above budget.

Best of luck,

Stuart