what will my comression ratio be with a stock bore sbc 400 with forged dome wiseco pistons and a fresh set of 882 heads with 1.94 valves

 

Depends on the domes.

It's a bad combo no matter what domes.

 

why is it a bad combo?

 

882 heads are not good, they are junk smogger trash, that are know to crack and have small ports and huge chamber. Never crutch such a head with dome pistons, the engines efficiency goes to hell.

 

according to 4 different engine shops in my area they were the next best thing to doublehumps. I can not afford high performance heads. I am getting these for 100 bucks with new valve job. I am not trying to start a fight here I am just stating what I was told by someone that has been in the machine shop bussiness for 17+ years.

 

They are garbage. In fact, I have personally thrown a rather large number of them in the trash; some figuratively by sending to the scrap iron dealer when convenient, some literally when it wasn't.

There is no "next best thing to double-humps".

Don't waste a dime on them. Anyone who tells you those are performance heads, is not to be trusted.

I'd suggest, as a budgetary measure, that you scale your pistons back to flat-tops or even dishes, and consider hypereutectics or other less expensive ones; and use better heads, with smaller chambers. Power comes from heads, not pistons. Put your money where it does the most good which is in the heads.

 

Think about it, you're getting them for the cost of a valve job.

 

I am only getting them for that price because I bought the sbc400 block,crank, wisco pistons, and I-beam rods from him. he had them priced at 300. there are alot of dirt tracks in my area and alot the the racers in the beginning classes are running these heads as well. I am not looking to get 600 HP I just want a decent street engine that will be good red light to red light. I doubt it will ever even take a trip down the local dragstrip.

 

They run them because class rules require them, not because they are good. That's how they equalize the cars, limit their speed, and keep cost down; not make them fast.

 

well can you tell me another set of heads I can use with a big enough cc so I will be able to use pump gas wtih this motor. I figured I would have to use 76cc heads to get my compression ratio down low enough to use pump gas. I am not sure if my compression ratio will be low enough with the 76cc heads. I was just trying to figure out if this setup would work on the street with pump gas, not get into a head bashing contest.

 

What would be a good choice of heads, then? Does GMPP make a decently-priced set?

 

Well, that would depend on the domes, then.

For a cheap set of heads that will run good, look at the Vortecs; especially if you're buying an intake at the same time. Run a small enough cam that you avoid having to modify the heads. You can pick them up at the junkyard fairly cheap, if you ask for them right; ask for heads off of a 96-98 pickup with a 350 (not a 305), and DON'T utter the word "Vortec", or say anything about performance. You just want the right heads for your construction company's truck, is all. The casting numbers to look for are 906 and 062. Accept no others.... above all not 70s smoggers, that made 400s put out 180 HP.

 

well all I have is what I mentioned in the post. I still have to buy everything else. waht is so special about the vortecs? I have heard alot of talk but know really explained why they are so good.

 

also will I have to do anything other than a basic valve job to get them to work. I know that machining them always makes them better but, waht I am asking is will I get decent performance gain over the 882s just bolting them on?

 

You've gotten off on the wrong foot. Slight dished pistons with 64cc Vortec or L98 heads would produce good pump gas compression. You still haven't said what domes are on the pistons, but to get good 76cc heads, you're going to have to do something like World Sportsmans or Pro Toplines. It might be cheaper to get them to exhange the pistons and go to the JY for the Vortecs - er, "96-98 pickup 350 heads".

 

Since you already have dome pistons your pretty much screwed. Just get the 882's and learn from your big mistake. Your not going to make lots of power but with 400cid you will have some fun. Just don't race anybody more then 100 yards.

Anyway what is the purpose of this motor, street, strip, whats it going into, what tranny...?

 

What's different about the Vortecs, is their intake port. It's raised. So the incoming gases have a MCUH straighter shot at the intake valve. They don't neck down and then make as sharp an angle as they do in those old smoggers. Since power comes from flow, and flow lives in the heads, they're a killer street part; the down side is, they're truck heads with 10-pound valve sand valve springs not much stronger than that and big guides that the retainers slam into at ridiculously low lifts and pull-out studs. They're set up as entirely anti-performance as they come. It costs near as much to make them into a semi-"performance" stock head, as it does to buy real "performance" heads. So the trick is, to work within their limits, and get the most out of them you can, without spending alot of money on them; and they'll give you close to 50% more HP than a bunch of 70s smogger turds, for about the same price, if you do it right.

Incidentally, some of the round-track motors I used to build, had all sorts of rules like that to limit the motor. Everything from "claimer" classes, where if you won or maybe finished top-5, you had to sell you motor for a set price (usually about $50 more than you could pick up a junk 350 for at the yard.... I avoided building motors for those guys) to "lift rule" to "valve spring diameter" to actual cam part # (usually the 929.... a smogger non-perf part much like 882 heads, in fact those heads were paired with that cam in all of the 165 HP 350s and 180 HP 400s throughout the 70s) to Holley 350 2-barrel to carb "claimer" classes. Just because I built motors for circle-track racers that had to run a 929, didn't mean that I thought it was a great idea to build it for myself to go fast, or that I advised paying customers to do that, like those shysters you're dealing with did to you.

 

Oh, I get it... It's a way to even out the playing field a bit, so it's a more accurate test of skill - not just a killer budget.

 

Exactly... look at NASCAR sometime for a good example. 358 CID limit, single 4-barrel, 3400 lb minimum, etc. etc. Every class of organized racing (well almost... F1, WOO maybe are exceptions) has stuff like that.

 

the reason the 400's in the mid 70's made 180 HP is because they had 8.5/1 compression and a junk cam. look at the 70 model 400 4barrel motor came with 10.25/1 compression and 330HP with 410 torque. So to me that tells me that cam and compression can do a lot!!!

 

I know that in Autocross, I run in F-stock (F-body, F-Stock, nice little match, eh?) but if I mod the car beyond certain limits, I go to E-Street Prepared. Then I have some more mods I can do, then I go to... Street Modified or something like that. And the whole time, the competition gets faster and faster. Even a simple engien swwap can bump you a few classes in a heartbeat, unless no one catches it... If you aren't beating everybody, no one really minds, though.

 

That was a big block engine.

 

well the info must have been in the wrong place in the shop repair amnual I was looking in at my friends repair shop cause it was in the list with all the 400 sbc from 70-74

 

The 70 model motor was "rated" by a different method, that didn't involve measurement. In 1971, when the federal government standardized the HP measuring methods, the 400 2-barrel's HP (that's the small block version, not the 400 4-barrel you quoted which is actually a big block) went down to 180 HP.

It was built out of 882 heads. The cam was the 929. I remember those parts well, by part number.

 

The factory never used the SBC 400 as a performance engine.

Period.

 

from what I understand, I am gonna have like 11/1 or 11.5/1 compression with this set up. which is to much for pump gas right? so what can I do to lower the compression ratio? I am using the parts listed, I already have them and can not afford to buy different ones.

 

can I please get some help with my actual question. I just want to know if I am going to have to sell these pistons and go with flat tops or if I can make the combo I have work. lets say I have a 5000 dollar set of 76cc heads instead of the 882's. just forget I ever mentioned 882's lmao

 

You can get hi-perf heads with 76-ish CC chambers on the aftermarket. Lots of companies make them. None come to mind right now, but I have seen them. You would be better off to sell (return?) your pistons for flat tops and get some 64cc heads though.

 

I am asking if my setup will work with pump gas? I am not concerned with heads and the quality there of. I just need to know if I can run pump gas with 11/1 or 11.5/1 compression and if not what can I do to my existing heads to get my compression lower so it will work with pump gas

 

How the hell are we supposed to know what compression ratio you have, you have not said anything about what size the dome is. What heads gasket you will use and how far the pistons are down in the cylinder.

I'm gonna take a stab and say its anywhere from 9.5-11.5:1.

 

I just said it sould be between 11/1 and 11.5/1 campression ratio, I am new to this, I have no idea what head gasket, I am asking for an estimate not an exact measurement. I never meant to have a debate over heads.

 

I have no way of knowing waht size the dome is exactly, they are in a different wiseco box then they came in and the only thing stamped on them is the size bore they are for. it does look like a good size dome

 

Take everything back and get the proper parts, thats the best advice i can give you. You don't want those pistons.

 

I can't take them back, I did not buy them from a dealer but from a local dirt track racer

 

Then sale the to another racer, those pistons will trap yourself into a corner and bang your head against the wall. Then get some dished hypereutectic pistons and some Protopline 906 vortec heads.

 

well unfortunatle I dont have the budjet you do, I am over trying to get an answer. Just because you don't like what I am trying to use does not mean you can't answer my one question thanks for nothing.

 

Selling those pistons for $400 will do you wonders. Hyper pistons $200 Protopline 906 heads $450. So you just need $250 or so minus $100 for your 882's you don't want and that only $150.

 

Send a pic and post it, measure the dome ht, look on a site that lists different Wiseco pistons.

 

where can I get pro topline heads for that price ? I just want this over and have my engine in my car I am to impatient

 

how do you measure dome hieght??

 

www.protopline.com

www.competitionproducts.com

www.shaverheads.com

 

I don't suppose you have a digital caliper, or any other type of caliper do you?

 

I am sure the guy I bought the stuff from does

 

Look on this site and find the piston that looks most like yours and then use the CR calculator on the same site to try to come up with at least a ballpark idea of what your CR is.
If it's over 10.5:1, forget it.
That doesn't allow for much dome though, cause a flattop piston with 6cc reliefs is 10:1.

http://kb-silvolite.com/calc.php?action=comp

Post what part# or a pic of the pistons that look like yours, I wanna see what your buddy sold you.

 

There should be some part numbers on the pistons, what are they?

 

See, you need to stay away from that guy. He has steered you wrong enough already.................

I agree with ME Leigh; sell the heads & pistons to get the proper parts.

 

thanks for the help. I don't have th epistons here with me, they are at my dads garage. I will get them tomorrow and try to get you all a pic downloaded. I am going to go t obed gotta early morning coming.

 

go to ebay and do a search for this item number 7931253209 the ones I have are barly (if any) bigger then these. I tried to post a link but couldn't

 

Those have +.150 dome 0cc, not good if yours is even more. Your CR is gonna be pretty damn high, above 11:1. Get rid of them.

 

dp