Thread: 305 TBI to 350 intake won't bolt.

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Hi Guys, I'm new to this forum, My son has a problem. He has a stock 87 chevy 4x4 with a 305 TBI. He was mudding and ran it into a deep water mud pit, it died. he tried to crank it in the pit, water came pumping up through the throttle body. He didn't know better. we yanked him out and towed the truck to his High school auto shop. He drained it changed the oil and fired it up but it knocks real bad and backfires up through the TBI. and of course everything is full of water.

Now he also has a engine trans and transfer case from an 86 k5 blazer the engine is a 350 4bolt targetmaster engine. he has both engines as school now. the plan was to put a mild rv cam in the 350, and put the TBI and manifold on the 350. Throw all the blazer stuff back into the pu truck and live happly ever after. got the cam in and today went to put the tbi and manifold on the 350 and he said the bolt holes don't line up.

We want to run the TBI on the 350. Why won't it bolt up. any advice would be appreciated.
Thanks

Newer SBC's have the four center bolts going straight down into the heads, if that's the problem you may have to use the 305 heads on the 350.

The 305 is 87 for sure. The 350 is 86 or pre 86. That may be the problem. I haven't seen it , just my son's discription. Will the 305 head work ok on the 350?

To use a later '87-'95 manifold on earlier heads you must simply elongate those bolt holes in the manifold a bit with a dremel tool or die grinder. A dremel bit chucked into a drill would even suffice. I've done it plenty times.

Camaro is 100% correct just slot the holes u may have to make a wedge washer to counter the angle of the bolt now. A piece of round stick 5/8- 3/4 drill a hole through it then with an angle grinder then on one end cut it to the manifold angle.

This does not work on all SB Chevy intakes And great care needs to be taken when doing this .

Is there a down side to using the 305 heads on the 350? At least they would bolt up.

I'm running 305 heads on my 350, but both were of the Vortec variety, so they simply bolted on and so did the intake. The only downside is that you lose a little top end breathing, but you also pick up some compression..........maybe a point or so.

Don

There is allways a solution to every problem. It usually involves a credit card though.

Originally Posted by Itoldyouso

I'm running 305 heads on my 350, but both were of the Vortec variety, so they simply bolted on and so did the intake. The only downside is that you lose a little top end breathing, but you also pick up some compression..........maybe a point or so.

Don

Years ago I put 260 heads on a 350, not good my exhast pipe glowed red. Finally sucked a valve.
I think I may just give the 305 heads a quick look over. Maybe lap the valves and put seals in it. I'm worried that the valves may have got bent when the water got in the cylinders.

The TBI 5.0 305 Heads have smaller 1.84" intake Valves to the 5.7's 1.94" . And the 5.0 305 Heads have smaller 58cc Chambers to the 5.7's 76cc This will push your C/R near 10.1 They will work fine But you will need at Least 89 Octane Fuel .

Ok , I don't like the idea so much now. What about this. Can I put an adaptor plate on the 5.7 4barrel manifold to use the throttle body on it. Or am I just opening up a can of worms. The kid has no money and I'm trying to get him up and running with out costing a fortune. Maybe the elongating the holes is the way to go. I appreciate your opinions Thankyou.

Originally Posted by camaro_fever68

To use a later '87-'95 manifold on earlier heads you must simply elongate those bolt holes in the manifold a bit with a dremel tool or die grinder. A dremel bit chucked into a drill would even suffice. I've done it plenty times.

So you're saying the angle is the same you just need to move the hole over a bit? My son said it looked about like an 1/8th of an inch or so. I'm a welder so I have burr or die grinders. I can send him to school with one but I don't know how receptive a High School shop teacher will be to this kind of modification in class. I think I like this solution better than than switching heads.

Using the 305 heads is asking for trouble---too much compression for the intended use. Slotting the intake holes to fit the heads is a very simple task that about anyone can do. The four middle intake bolts go in at a 72 degree angle verses pre-87's 90 degree angle.. That's the only ones that need modifying.

The holes are in the same place, just the angles of the the 4 center holes are slightly different.


I've done this mixing and matching many times---especially pulling the TBI intakes off the 80's Camaros and going with a regular intake and carb.

Camaro Fever I have Just done an Early Intake on the TPI Heads Build . You make it sound so easy . You do not want to just Hog them Bolt holes out . It will be Harder on the TBI intake because it's Thicker . Still when your Done the Bolts are on the wrong angle and you need to us Big Washers with half of the Head of the Bolts down . Here is the one I did http://shadetreemechanic.activeboard...picID=19075969