Dynoed Hawk 525 today, had a problem...
 

Dynoed first engine today. With Mercury Thunderbolt ignition on, engine would rev up to 5000 RPM, the we would lose ignition.(back fire through carb) Did this 3 times in a row. New coil, sensor,cap and rotor from mercury. Does this system have a rev limiter in it??? How about in the module? Its a v8 module.... Put an MSD distributor in with a 7AL box, and engine ran perfect! Right to 5700 RPM not prob. Anyone have any answers? Need to figure this out by Monday cause engine is coming off dyno Monday afternoon.

If you're referring to a Hawk 525sc, what was your total advance?
And is it a T bolt IV or V. The Vs all had a rev limiters built in, IVs did not.

Its because of the thunderbolt...THEY SUCK !!!!!!

[QUOTE=rdoactive;3094982]If you're referring to a Hawk 525sc, what was your total advance?[/QUO

It is a 525SC...28 to 30 degrees with the merc thunderbolt ignition back firing at 5000 rpm.(3 times) then installed the msd . It ran good . So we advanced to 32 then to 34 and the ignition never cut out. The HP kept climbing.....made 583HP at 5500RPM w/ msd. BTW, diff camshaft than stock from Hawk. Comp Cams cam. , this thing made good power for a 454 with a little blower!!! Had smaller pully, but never even used it. 583 HP at 5500 RPM was with the stock pulley.

[QUOTE=kreed;3095075]Readin back on your post, not sure if its a V or a IV. How can I tell ?...By the huge back fire at 5000 RPM?????????????????Very scary.......

Those engines run pretty high CR, and if I remember only reccomended only about 26 degrees. I did run about 28 with a smaller pulley, a V6 Tbolt IV, on 93 octane.
The V6 module gives a lot more initial timing. Hoping you're using bushings and light springs for a short advance curve with the MSD distributor.
Check the PN on the Tbolt module, mine reved over 5000rpm, no problem.

[QUOTE=kreed;3095075]That sounds good man. I have the same setup. 454, dart aluminum heads, 741 roller cams, 177 blowers, stock pulleys. They make nice power for some little motors! Compression on the hawk 525's were around 8.5:1 i think. Which is where i am with mine. I use a msd ignition.

Im sure it could have been something like a bad pickup in the merc distributor, etc.

If its a stock rebuild its 7.5 to1 cr and mercury recommends 35 degrees total timing if I remember correctly. If hawk ups the cr I would start with the 26 to 28. we have one here local with 36 total but it has a superchiller.

Its 8.5 to 1 Comp. started at 28 degree timing and went up from there. Ended up at 34 degrees, still only making 4.55 lbs boost. So thats where the engine made most power. It just started to fall off at 5700 RPM. Dyno guy said engine is in no danger at 34 degrees.

[QUOTE=MILD THUNDER;3095129]I guess it could, but Pick up is brand new!

ttt

I can only imagine what your thoughts were when it blew back up through the carb at 5,500. The last dyno session I had the exhaust tubing blew off one side at about 6,000. Scared the livin **** out of me. If your using the stock ignition from a 525SC then it should have a rev limiter built in however I thought they were set internally at 5,250. If you could only find another distributor to rule the back fire out would be helpful. I know a lot of guys using that ingnition flawlessly however if you plan to run above 5,250 then you'll have to see if you can send them out to be changed. The rev limiter wouldn't pop back through the carb though, it only drops cylinders. Did you take the distributor apart to check for play between the shaft and the housing? I would get it dialed in with the MSD and go find yourself a good MSD set up. Not sure if that's what your looking for as far as an answer goes but you could be fighting this for a while and still not have what you really want.

They definitely like around 34/35 deg. Sounds like a great package, the little 177's do pretty good on a 454. I did this one a couple years ago with Edelbrock marine oval port heads, stock 525sc cam, and 8.5:1 comp, stock carb with 95's front and rear.

Yea, very stressful! Lots of beer that day! Distrib shaft is fine. New pick up in distrib too. If there was a rev limit, it would be in module....right? Do all Thunderbolt modules have limiters in them??? Found a V6 module that Im going to try on the second engine on Wednesday....Or , can I use the thunderbolt distribs with Msd blue boxes instead of the modules???

you got some great numbers! I was really surprised w/ my 580 HP! I want you engines numbers! Mine made at least 600 FT LBS through 4700 RPM. We have small jets in front at 87 and 96 in rear. Second engine going on on Wednesday...........

Make sure the ground is good on your Merc ignition box. The only difference on the Merc boxes is the advance curve...no impact on a dyno testing. The Merc ignition system should work flawlessly to a least 6000 RPM.
Were the same plug wires used on both distributors?

The MSD should be plug and play and also the Cranes. With either one of those you wouldn't need the module. I am not certain what TB systems have the rev limiters. My TB 1V's did not. I hate to give you any wrong info on this as I know your time spent is important you have everything ready to go for your next session. I would PM Griff in regards to your deal here. Did you confirm what you have. TB 1V or TB V. So your components you currently have are Dist, Module and Coil, correct? No ign. boxes of any kind. Just want to make sure you have all the correct components and your not missing something. I thought I remember a TB system I had years ago on a 525SC having an additional box. That was back in 1993. To many buds since then. PM Griff, I'm sure he'll answer your questions.

I am going to put together some budget build SC's and wondered if you used the stock/original rec port intake or did you use an oval port? Unless otherwise this was not the Merc 525/177. Did a lot of back to back testing on this years ago with NA engines.

plug wires were the same. Maybe my module is bad????

Used stock stuff like u said, no extra box. Used rectangular port intake. I think these are original blowers that Hawk put on. They do not say Merc SC on the sides.

The original intake was badly corroded at the Tstat housing which seems to be very common. I replaced it with an oval intake and the factory blower with stock pulleys.

The Hawk 525's were Merc 420's with the 177 blower. Not sure if they have a rev limiter or not. Most likely they do, but it should not kick in until at least 5300-5400rpms if it is the stock 420 ignition. when it kicks in, it is more like an engine miss, but it should not create a carb backfire. I did some prop testing on my 525SC Pantera and hit the rev limiter a few times. It really was not that significant. Just felt like a slight misfire for a split second.

I agree, the rev limiter will not cause a backfire like that..something in the ignition was failing...

I've hit the limiter on the dyno a few times and it's pretty smooth. For it to be shooting through the carb, assuming your timing and air fuel was in range, it's got to be misfiring. The modules are very ground sensitive and I've definitely seen issues in the past from a bad ground. Hope it works out for ya! :drink:

What turned out to be the problem? I saw in the cig forum that it ran very well on saturday.

[QUOTE=MILD THUNDER;3095129]What kind of power are your motors making? Just curious because I am picking up a pair off 525 hawk motors with intercoolers and putting them on my 454 mags.
Wayne