I'm putting a 305 TPi from an 85 I-Roc with a T5 and a shortened TA posi rear in an 80 Triumph TR7 convertible.

I would like to get the most affordable horsepower out of this motor by mainly raising compression to 11-11.5:1 by decking the block, plaining the heads and 350 headgaskets(or something else that's thinner than the 305 gaskets) , headers, no cats, good cam, porting the intake and plenum myself, adjustable FPR and a custom programmed EPROM.

What is the maximum possible HP with this combination of mods?

Back in 89, when I was 15, I put a 4 barrel carbed 305 with 700R4 in an 80 TR7 and it was quite fast at 8:56 in the 1/8th but this time I want MORE power.

Below is a pic of a TR that I will duplicate the look of and for those who dont know what a TR7 is, this is it.

Thanks in advance for any input on the power potential of the 305TPI

 

theres no answer to that because you don't give specific parts. You could go real radical and buy good heads or you might just use pos lg4 heads.

why in the world are you putting in a 305 and not a 350 if your so concerned about HP. They cost the same.

 

That TR7 is damn cool!!

Honestly, I would install a bone stock 305 TPI(Which will be very cheap to find COMPLETE) and spray it with a 100hp worth of nitrous. Then i would also do the usual bolt on modifications like 1-5/8" headers and a matching Y-pipe and a decent exhaust system behind all of that. Port match the intake manifold parts or upgrade them to better parts if funds allow. It would be a VERY quick combinations that wouldn't have you focusing on modifications to the engine internals(which would cost a lot and not get good results as efficiently).. If you get greedy for power, use 150hp worth of nitrous. Keep it tuned slightly rich for safety. If it does damage itself, no big deal...Just buy another 305 TPI and replace it(again, it will be very cheap)....

Sounds like a good project! If those cars weigh a LOT less than a thirdgen camaro, a sprayed 305 with bolt ons would be an 11 second car easily...hehe

 

AutoRoc

These cars do weigh a lot less. The 85 IROC has a gross vehicle weight of 4280lbs and the TR7 has a gvwr of 2954lbs which is a difference of 1326lbs. Ofcourse the IROC can carry 2 more people so the GVWR difference is skewed by about 300lbs or more so the actual weight diff is more like 1000lbs.

I dont want to spend the extra time and money to get a 350 cause I bought a ragged out 85 IROC for $200 so I already have the 305, harness, computer, TPI and all the sensors.

Basically I just want to know if I can get 275-300hp through raised compression, headers, cam, custom chip and porting the plenum.

I dont know which cam and headers but will this HP goal be achievable if I were to use this combo of mods with the right cam and headers?

Is this possible without buying a $1000 pair of aluminum heads or would I need to get some L98 heads?

If this is not possible, I will plunk down an extra 200-$300 for a 350 at a salvage yard and build it.

 

Possible, but it's gonna require a good bit of work to those heads I think. Port work will be essential....

 

4280 lbs

That listing on the door jamb sticker is max capacity, that is, vehicle weight, plus passengers, plus cargo. Actual vehicle weight is closer to 3250lbs.

That carbed 305 you put in last time was only rated at about 150HP, while the TPI 305 you have is rated at 215. A good set of headers and full exhaust with a Holley StealthRam conversion should put you right around 275-285HP. No heads/cam needed.

 

Don't the 85's have that expensive MAF Burn-off Relay and the really slow ECM? If it were my car and engine, I'd get the TPI parts off of the 305, get a 350 long block with a nice cam and decent heads, convert to Speed Density, program my own chip, and be done with it.

 

From my experience the with the LB9 305 they start pinging even with the knock sensor if you use 87 octane gas. I would think the L69 would be similiar. I wouldn't bump the compression up to much. You would probably get more gains by porting your heads.

Porting the heads and putting a comp cams xr roller cam or a zz4 cam would probably get you around the 250 hp range at least.