I have been doing a lot of reading on here because I wanted to swap in a tpi system on my tbi truck but the problem is that my truck has the 4l80e. The truck is a 91 crew cab and I have a short bed and that was supposed to be my first project then the tpi. I know the truck is a sled and fuel mileage is not to realistic but anything is better than 11 mpg. Any way long story short a head gasket blew on #7 cylinder Friday afternoon and now I am facing having to tear into the engine sooner than anticipated. The truck is bone stock and my budget is very slim when I got the truck headers were already installed and bolt holes stripped in the heads. OK enough babbling and rambling. I have located a set of vortec heads and I can get an intake from ebay cheap enough so the big question is will I realize anything from the heads and intake or would I be better off to go ahead and change the cam and lifters too. I know I would be better off but really I guess what I am trying to ask is would I be wasting money by changing the heads and intake and not the cam as well. What flat tappet cam would be recommended? The truck has 157k miles on it and ran really well until it blew. I also have a 454 throttle body I could put my 350 injectors in if that would be a help. OK I think I hit all the high spots enough rambling. Thanks to whoever takes the time to read the ramble and reply. Scott

 

Low budget? Buy a used Vortec engine instead of fixing yours.

 

By budget I mean shoestring. Motor is in no way possible right now. I took the heads off today and it was only a blown gasket on #7 cyl no cracks. I read somewhere the other night about shaving the heads to up the compression. The heads are the swirl ports 10110810 heads. I just don't remember the amount to shave the heads. If I were to shave the heads and install 1.6 rockers do you think it would be worth while??? Anyone.... Bueller Bueller...

 

Are the heads in usable condition? Have you checked the valves and valve seats? Are the guides any good? Have you CHECKED the heads to see if they're flat?

Swirl-port heads aren't worth a fart in the wind. If you can't plane 'em and throw 'em back on, you might as well get something else. Plane them enough to get them flat again. No need to go further.

1.6 rockers won't fix what's wrong with swirl-port heads.

 

Well I ended up having the heads cut .025 and I have the fel pro 7733pt2 head gaskets which compress to .039. If anyone can tell me what the quench and compression ratio will be like this please let me know. This is a bone stock 91 truck TBI 350. The 1.6 steel rockers should be here by noon tomorrow and I hope to drive the truck home tomorrow.

 

Nobody can tell you quench and compression ratio with the information you've provided to us. Some might make guesses based on "typical" information.

Cutting the heads doesn't change quench, but does change compression ratio.

Is the new gasket thicker or thinner than the old one? How far down are the pistons in the hole? First Guess: Your quench distance is way too large.

What is the chamber cc of the cylinder heads? Are the chambers all the SAME cc?

Did you ever verify that the valves actually seal, and the guides aren't wiped-out?

I hope you remembered that the TBI engines use rail (self-guiding) rockers, if you ordered ordinary ones you're screwed. There's nothing else to guide the pushrod/rocker.

 

I replaced all the valve guide seals and checked the valves and guides. They were in good shape. I did not cc any of the holes on the chambers. I did get self aligning rockers. I have no idea of thethickness of the original gasket.

 

#1 If you didn't open up the pushrod holes,you will have interference w/ 1.6 rockers.#2 A .039 gasket is gonna set your quench @ approx .064".It should have had a .028 stock.That is way too much,especially with the increase in CR from cutting the heads.If they removed .025 from the heads,that ='s to approx 4 cc less chamber volume.1cc for every .006" removed.You did do both heads,correct???There seems to also be some conflict as to the actual chamber volume of 810/191 heads as wether they are 76cc,or,64,65cc.I would cc @ least 1 chamber to verify & I definitely wouldn't try to use that .039 gasket.You CR could be anywhere from 8.5:1 to 9.4:1,depending on the actual chamber volume.Your engine should have 8.75:1 stock assuming it is a 3/4 or 1 ton.

 

Opening up the pushrod holes is a simple task by simply drilling them out with a 1/2" bit to provide clearance for the 1.6 rockers,but,you have to do it with the heads off,or you risk getting shavings in the engine.

 

Yes I did do both heads and I was at the fire station yesterday and really had no way to cc the heads. Do you know what fel pro part number I may be able to get for a gasket?

 

I don't have the Felpro #,but,the GM gasket is #14096405,or,#10105117.The parts store should be able to cross reference.These gaskets have a .028" compressed thickness w/ a 4.100" bore.

 

Thanks for the info.

 

That second number crossed to what I have so I am just gonna put it together with those. We have snow and ice coming today and I have to get the truck back running cause my 69 firebird does not like wet weather much less ice...

 

Those #'s do not cross reference.The Felpro # 7733 pt 2 is a .039" x4.125" gasket.It has .011" thicker compressed thickness & a 4.125 bore.The #'s I supplied are both .028 x 4.100.If you use those,your quench is gonna be approx. .064".

 

I checked the heads 60 cc

 

Is this a 3/4 or 1 ton? If so,it prolly has 18cc dish pistons which is gonna put your CR @ approx 9.1:1 with a .028 gasket.If it is a 1/2 ton with the 12cc piston,you'll be around 9.6:1.With a .039 gasket,your looking either 8.9:1 or 9.3:1,depending on actual piston dish.

 

Here I go again... typed this once and got a call and wiped it all out... Yes it is a 1 ton crew cab truck. If it helps with piston ID there were two v grooves in the ridge around the outside edge. I had the local parts house run the numbers you gave me and the second one crossed to the numbers I had. I realize this is not the ideal gasket for my application but I had to get the trunk back together today. I fired it up about 1:00 and after adjusting the valves and double checking it all I took it for a drive about 2:30. I can't really say it is any stronger running because it ran so strong before. I guess the gas mileage will tell the tale on the rockers and little more compression. Thanks a lot for all the info. Scott