Need help guys, engine gurus PLEASE!
 

I'm converting a bracket car back to street,had a car accident last year and now have 4 fused vertebres & a plate in neck.can't drag race but still want to enjoy car on street,car shows etc. here what i have 69 camaro all steel now 468 12.5:1 crane r274 nitrous roller cam 737 lift.990 heads 5000 stall protree brake th400 12bolt w/4:88 gears.msd 7al3 elect. 1050 domn.I'm changing stall to 3500.trans to built 400 and gears to 3:73's my question is eng? cam to large? pistons to large? for street?Any and ALL help would be great THANKS IN ADDVANCE MARK B. DALLAS TEXAS https://www.yenko.net/ubbthreads/imag...lins/dunno.gif https://www.yenko.net/ubbthreads/imag...lins/dunno.gif

Re: Need help guys, engine gurus PLEASE!
 

That setup would be fun to try to drive on the street but I doubt that you will want to feed it the expensive gas that it will take. Not to mention the traffic in Dallas is horrific at times.

I would recomned a much milder cam and lower compression if you want to drive it very much on the street. What you have now is going to be pretty limiting and will have no low end with a 3:73 unless you change the cam. A good street cam is someing more along the lines of a L-78 for everyday use. Wild cams get real old on the street unless you are just going to the 7-11 and back.

If you have a back conditon why not go to a good hyd cam and 10 to 1's. With those cubes and in that light of car it will still run dam good with out killing your back.

Re: Need help guys, engine gurus PLEASE!
 

I've driven her on the street but. its nothing but extremley loud and useless on street tires.wasn't sure how cam and eng would hold up to street driving.I heard some big blocks back in 69 were 12:1 motors but didn't know size of cams they used.going to pull the dominator off and go with a 4150 type carb.i guess i could fly cut down the pistons.eng is real fresh and didnt want to rebuild again. https://www.yenko.net/ubbthreads/imag...ins/3gears.gif

Re: Need help guys, engine gurus PLEASE!
 

Mark;

If you don't mind paying for the race gas, there's no reason you can't leave the 12-1's in there. I would swap out that cam though. I've ran the non-nitrous version of the same cam on the street and it's pretty rough on valvesprings, not to mention the potential for roller lifter failure in a predominantly low rpm street gig. (don't ask me how I know that https://www.yenko.net/ubbthreads/imag...lins/frown.gif )

Stepping down to a smaller roller will only sacrifice a little power but reliability will increase dramatically. You could also swap to a flat tappet solid cam...once you've cleared the break-in hurdle, chances are you'll never have to worry about it again. Obviously a flat tappet cam will require different springs, etc., but you can always sell off the roller parts to help finance the swap.

The 3500 converter and 3.73's should work fine with the right cam choice, but whatever you do, don't buy 1 of those "off the shelf" speed shop special converters, pay the money for a good Coan, Art Carr, ATI, BTE, etc. You'll be glad you did. Your motor should still be capable of wasting a generic converter with anything resembling decent traction, hence my recommendation for a good converter.

As far as the Dominator goes, you can clean them up to behave pretty well on the street, but gas mileage is never going to be a strong point. Dominators do peg the "wow meter" when the hood's popped at the car shows though. https://www.yenko.net/ubbthreads/imag...mlins/grin.gif Which model do you have?

Just so you know where I'm coming from, I was an engine builder/machinist before I went into my current business.

If you'd like any help with cam choice feel free to ask. I'll be glad to help.

Eric

Re: Need help guys, engine gurus PLEASE!
 

CONVERTER IS A GER.DOMNATOR IS A 1050 AND PISTONS ARE 12.5:1 CAM HELP WOULD BE GREAT!I HAVE READ ON CRANES WEBPAGE ABOUT TO MUCH COMPRESSION AND NOT ENOUGH VALVE RELIEFE COULD CAUSE DETNONATION PROBLEMS,GERNADEING ENG AS WELL.THANKS AGAIN MARK

Re: Need help guys, engine gurus PLEASE!
 

Mark:

Did you put this engine together? Has the engine been blueprinted? Which brand of pistons? Those 990s have a LOT of chamber, and if they're like the rest of GM factory heads they're gonna be about 5cc on the high side before cutting. A lot of times an engine doesn't have the compression you think it does. And, you could help *cheat* that compression down with your cam choice.

Looks like Eric can help ya get squared away! https://www.yenko.net/ubbthreads/imag...iggthumpup.gif

Re: Need help guys, engine gurus PLEASE!
 

Did not put engine together.a engine shop in louisana did the build.I believe there big in drag boat engs.Bought car in aug of last year.made 8 passes then had car accident in sept.

Re: Need help guys, engine gurus PLEASE!
 

Mark;

Is the current converter a GER, or the 3500 you plan on purchasing? If you're planning on purchasing a GER, please PM me first!

Do you know what the "list" number is on your 1050? There are several different 1050's available, some can be made to work well on the street while others can't.

As Rob stated above, those 990 heads have pretty big chambers to begin with. Unless they've been whittled down, they should have around 119-121 c.c chambers. Any chance you have the spec/build sheet from the engine builder?

The reason I ask is, the last 461 BBC I built for a customer had SRP pistons in it that were rated at something like 12.4 with a 119 c.c. head (been a while since I built that, but those #'s should be pretty close). I didn't have to flycut the pistons to clear the cam. With the pistons roughly .010 down in the hole, a .041 gasket and 121 c.c. chambers in the heads, the actual measured compression ratio came out to roughly 11.8. You can't always go by what the catalog says. Just a few c.c's either way can make a notable difference in actual compression ratio.

As far as the cam/compression deal, running too much static compression with a cam that's too small will build too much cylinder pressure and can lead to detonation problems. That's why it's really important to know the actual compression ratio when choosing a cam. At roughly 12-1, you still have room to step the cam down w/o running into this problem.

If your compression actually is 12-1 or slightly above, I'd look into something like the Crane roller p.n. 138121, which is .663-.638 lift (gross), 260-270 at .050 and has a 110 LSA. The duration is 14* smaller at .050 and you're losing roughly .074" lift on the intake and .088" on the exhaust. This will still have enough duration to work with your compression, but the reduced lift will dramatically improve valvetrain life. Power loss would be mild.

If you'd rather go with a solid flat tappet cam, look at something like the Crane 134691 or 131311 (256*-266* @ .050, .580-.600 and 256*-264* @ .050 and .618-.638 respectively) The 691 cam makes great power from about 4000 up and has a nice thumpy idle. The 311 cam makes great power from about 3600 up and has an absolutely wicked idle. Both are "streetable" cams, but they can be pretty choppy unless you've got the carb dialed in for part throttle cruising.

Sorry for being so long-winded, just trying to cover as many bases as I can.

Eric https://www.yenko.net/ubbthreads/imag...lins/beers.gif

Re: Need help guys, engine gurus PLEASE!
 

One of our L-72s came in at a lowly 10.2:1 (11:1-11.25:1 according to published info!), even after taking a couple thou off the heads. I've even heard of some rebuilt L-72s (all stock, no milling/decking) only having a CR in the high 9:1s!! If you have it torn down, cc everything so you know exactly where you're at.

Re: Need help guys, engine gurus PLEASE!
 

Rob;

Just out of curiosity, did it come in at 10.2 with OEM style steel shim head gaskets or composition styles? What did the heads c.c at? How far were the pistons down in the hole?

I agree with you 100000% about checking everything if/when the engine comes apart. If I had $1.00 for every "13.1" motor I've torn down only to find actual compression at 12-1 or less....well, I'd have a lotta dollars. https://www.yenko.net/ubbthreads/imag...mlins/grin.gif

Eric https://www.yenko.net/ubbthreads/imag...lins/beers.gif