5.7 350 chev gm help

hotrodford8 · KINCARDINE, ONT

5.7 350 chev gm help

chips · Veteran Member

www.crankshaftcoalition.com/wiki/Vortec_plastic_timing_cover_replacement

Simple Google search shows that (according to the post I linked) old style timing covers "can be made to fit" but are not "designed" to fit Vortec engines. I don't blame Karbelt for not having an answer for you due to the simple fact that those two parts were NEVER designed to fit together. "Can be made to fit" is not always good, I had a friend hammer a Ford 4 1/2 bolt circle wheel onto a Chev 4 3/4 axle .... he made it fit. I wouldn't have done it and I doubt it's too safe but the correct answer was "it could be made to fit" but that don't make it right.

As for your cam question .... "hi lift cam" is WAY too vague. What IS the lift? How deep are the valve notches in the pistons? How deep are the pistons in the cyl (at TDC)? How thick is the head gasket you are going to use?

Feel free to rely on someone else's opinion as to whether your "hi lift" cam fits your engine. I wouldn't. Too many variables. You'd be better off taking the time to determine your ACTUAL valve to piston clearance of your specific combination yourself.

"Hi lift" can mean 480 to some and 650 to others.

supernash · WEST PERTH, ONT

Don't forget the valve springs and pressure too. I've had to shim almost always to make all them get along even after flycutting the pistons. Kissing isn't an option.

Get yer plastasine in there with heads torqued. Felpro makes head gaskets with different thickness exactly for this.

Jus my 2 cents

hotrodford8 · KINCARDINE, ONT

thanks for the help will accept having to mod timing cover the question is fit for seals etc/ use roller cover with mods fit vortech block 4 bolt OK / have ordered parts / ; on cam flat decked block flat piston w reliefs, cam is 282/290 , 231/239@ .050 , 110 LSA , 535/550 lift , to 6400 rpm will this cam turn tq on down low ? PS will try to avoid hammer

chips · Veteran Member

hotrodford8 wrote:
thanks for the help will accept having to mod timing cover the question is fit for seals etc/ use roller cover with mods fit vortech block 4 bolt OK / have ordered parts / ; on cam flat decked block flat piston w reliefs, cam is 282/290 , 231/239@ .050 , 110 LSA , 535/550 lift , to 6400 rpm will this cam turn tq on down low ? PS will try to avoid hammer

Go to this site http://www.howardscams.com/ and use their "cam recommendation form" (purple box bottom left of page). See what they suggest and compare the recommended cam specs to the cam you already have. If yours is nowhere close to what they suggest, I wouldn't run it and would go with their recommendation unless you're just going for the "thump and raunch" of a big cam.

-- Edited by chips on Thursday 24th of March 2016 05:11:46 PM

RacerRick · TORONTO, ONT

Not really enough info for this motor but I will try.

That cam looks like a hydralic roller with the amount of lift and short duration and the fact its a late model block. I would be looking at a double spring on the head like Comp 987's. Its 130lbs seat pressure and good to about .620 lift. It also comes on Dart Iron Eagle heads.

I say Iron Eagle heads because Dart doesn't make Pro 1 heads in Iron - only aluminum. They do make the Iron Eagle in iron. Buy the 200cc head, and don't buy the S/S head as its a stock replacement head and the normal Iron Eagle Platinum is a much better head. At the compression ration you are looking at, get the straight plug version to avoid header issues. I would also look at the 64cc version, part number 10321112P with the springs you need.

Also, a flat top 350, zero decked, with standard 6cc 2 valve reliefs will give you 10.3:1 with a 0.038" head gasket, and also about the minimum quench distance. If you are using old school forged pistons like TRW's, go with the slightly thicker 0.042" thick head gasket to make sure the piston rock doesn't allow the piston to touch the head (can happen under .040" clearance). This should work well with the heads and cam.

The pistons are probably going to need to be fly cut, and good roller rockers and good pushrods are needed. That is way too much lift and spring for stock stuff.

The RPM Airgap will work well with this motor, but I would change the carb to a 750, as the large venturi on the 850's really kill the low rpm carb signal. Run a proform bod ont he 750 and it will flow more than the 850, and still have the smaller venturi for good low rpm throttle response.

I would also change the rods on this motor. I would probably buy a cheap set of SCAT rods for this motor. The stock powdered metal rods can break through the beam when leaned on. The older forged rods are much tougher and can also be swapped in, but after getting them resized and new rod bolts put in, you are pretty much the same price as the lowest price SCAT rods, which are made of a much better steel (4340 instead of 1053) and are not fatigued. Remember that boats are very hard on the bottom end of the motor as the motor can go from full load to free wheeling to full load in a few seconds if you pop the prop or pump out of the water by jumping a wake or similar.